She may be married, but will that stop her trying to bed old flame Chris Warner? That's the question on everybody's lips as veteran vixen Rachel McKenna returns to Shortland Street this Thursday.

Since she first flashed onscreen in 1993, McKenna has made many Madonna-esque transformations. Over nine years, the CEO's bratty, money-grubbing teenager turned into an allowance-scamming uni student, a boozed-up bar owner, a dressed-up HR manager, then went back to being a drunk.

When she got out of rehab in 2003, Warner had moved on with Donna, and a deflated Rachel left to work for receptionist-turned-MP Marg in Wellington.

Back at the hospital, there was no sign of that red bob until 2007 when, as a Ministry of Health auditor, she swept in and out of the clinic and Chris' bed, only for his wife Toni to discover them in flagrante delicto.

Gutted when Chris chose his family over her, Rachel returned to Wellington to marry businessman fiance Jeremy.

Now, leaving her husband behind, she suddenly turns up at the hospital as DHB supervisor: to suss out whether ham-fisted CEO Callum is the man for the job and sort out the squabble over the cafeteria contract.

That's the official reason, but why is Rachel really back? On TVNZ's Shortland Street site, a poll lays out the options: to bust up Chris' relationship with Gabrielle; to replace Callum as CEO; to make cuts at the hospital; or to catch up with old friends.

There's no doubt she'll try the first and the third – perhaps the second – but whatever she does, she's sure to put a few noses out of joint. With that trademark temper as hot as ever, Rachel clashes with Callum (who's not happy about having a minder), with Kieran (she's not impressed he's dating a schoolgirl), and odds are there'll be some sparring with fellow femme fatale Brooke.

Then there's the inevitable head-butt with Chris' fellow-surgeon girlfriend Gabrielle, who has Asperger's.

"For a while, she's really nice to Gabrielle, which unnerves those who know Rachel, because she's quite tactical," says Angela Bloomfield of the character she knows so well.

Bursting with the bitch-is-back secret all year, Bloomfield, chatting between scenes at Shortie HQ in West Auckland's Henderson, is glad she can finally spill.

Frank and funny, the diminutive 36-year-old (she's three years older than her character) has been directing Shortland Street for five years, so she's hardly a stranger on set.

But that's made it even harder to keep the comeback quiet. She's relishing a return to the flawless makeup, flame-red hair and playing dress-ups: her new pencil-skirt style is somewhere between Brooke's clingy clothes and Libby's "corporate girlie" look, Bloomfield says.

As she speaks, a Rachel scene flashes up on the giant screen behind us.

"Hey, there I am now. Weird!

"It's a bit intimidating seeing myself on screen again," she admits.

"I don't look like these photos [see box] anymore, and it's taking a little getting used to. I go 'What's that thing between my chin and my neck?"' she says, pointing at an imaginary double chin.

The woman dubbed Shortland Street's sexiest-ever female hardly needs to worry.

Chris certainly thinks Rachel's looking hot, although he quickly lets her know he's got a girlfriend.

"Then Rachel lets him know 'Well, I don't really give a shit about that. That ain't going to stop me,"' says Bloomfield.

"He certainly doesn't avoid her – he gives her a little bit of bait – so she just goes for it."

Yes, she admits, there'll be plenty of will-they-or-won't-they – just like back in the day (2002) when Chris and Rachel first got together.

They were an item for just a year, which is serious commitment on the sped-up Shortland Street clock.

"Rachel's never really got over him," Bloomfield tells me.

"He's the love of her life. The one who got away."

Coming from similarly schmoozy Auckland-aristocracy families, and just as wilful as each other, Rachel reckons they're a perfect match.

"She might have rose-coloured glasses on, but she thinks he's strong enough to fix her. To save her."

From herself – and from the booze. A tall order for any man. But Michael Galvin, who plays Chris Warner, reckons that, from a long list of exes, Rachel is Chris' best match. But he's not counting out Gabrielle. After all, not every couple can play mental chess while performing surgery together.

Still, will he be able to resist Rachel? And when her husband turns up at the hospital, will that love triangle become a quartet? When the cameras aren't rolling, Galvin and Bloomfield are more like brother and sister than on-and-off lovers.

They're both married with children: Bloomfield and husband Chris (yes, it's the same name) have Max (5) and Maya (nearly 4), while Galvin and wife Melissa have Lily (3).

Years ago, Bloomfield unknowingly played Cupid when she took both Galvin and her mate Melissa to a party; the best friends were bridesmaids at each other's weddings.

This time round, Rachel and Chris haven't shared any bedroom scenes – yet – but Bloomfield admits they're always weird. She laughs remembering the last such scene, when she wrapped herself in a bed-sheet "cocoon" to preserve her modesty.

"I got home and Chris asked 'Hey honey, how was your day?' and I replied 'Oh good, slept with Michael'."

There have been numerous calls for that cocoon over the years. Not even Bloomfield can count the notches on Rachel's bedpost, though she gives it a go: Stuart (aka Martin Henderson), Rangi, Chris, Manny, a few doctors (Frank, Adam, Stephen), a nurse (Cameron), Zac the barman, and bi-polar Jack, who kidnapped her and tried to stage a mock wedding.

Over the years, Rachel's said "I do" three times – to doctor Daniel Buchanan and to current husband Jeremy – but you can't really count her marriage to hapless friend Nick Harrison, which was a student-allowance stunt.

The truly unbelievable happened three years later in 1998: not when Rachel got struck by lightning, but when she came out of it in love with Nick.

"So he made a turn-her-off tape where he sat in the bath farting and ate onions, and she thought it was delightful!" Bloomfield says with a laugh.

When they finally went to bed together, she turned off the light and got an electric shock which jolted her out of her lunacy.

"Like something from Days of Our Lives – just without the amnesia! But the most ridiculous storyline was 'Rachel has nits, let's stage an intervention'. I can't believe they ended a Friday episode on that! Did they really think 'Oh, that'll keep them going over the weekend!"?

Usually, though, she got landed with the "issues" storylines. Think anorexia, bulimia, sexual harassment, chlamydia, getting kidnapped, nearly drowning, surviving a car crash and a house fire and, of course, alcoholism, to name just a few.

By 2002, when Rachel got her tubes tied without consulting Chris, playing someone who'd practically shake a baby felt all wrong to Bloomfield, who wanted a family. And it was hard playing someone so hostile, caustic and aggressive day after day.

"I'd walked down that road for quite a while." When the writers wouldn't adjust the character, she decided it was time to shrug off her increasingly self- destructive alter-ego.

"I'd been immersed in the Shortland Street world for so long that there was some cathartic behaviour that needed to go on. I was figuring out who I wanted to be again."

That turned out to be a mum and a director, of both Shortland Street and TV2 dramas Jackson's Wharf and Go Girls, as well as an actor.

Fast forward seven years and you can see why the show wanted Rachel back: fans both past and present are clamouring to see what she'll get up to. But why did Bloomfield decide to slip back in front of the camera?

Well, in 2007, after her Chris-bedding cameo for Shortie's 15th birthday, the are-you-coming-back questions got more frequent.

Meanwhile, playing loud-mouthed solo mum Shona in TV2's shortlived boyracer drama Ride With The Devil, for which she earned a best-supporting-actress nomination at the 2008 Qantas Film and Television Awards, reminded Bloomfield how much she missed acting.

"I enjoy acting no matter how long the day or how traumatic the moment," says the star of mid-90s films The Frighteners and Bonjour Timothy.

"There's a ridiculous kind of euphoria of releasing your emotions, getting it right and affecting someone. I liken it to that good golf shot you lop down the fairway, just nail it and it goes straight in the hole."

And, after seven years without Rachel, she was ready to take her back.

"Because I started as Rachel so young, I almost did it without thinking, and now I'm doing it with thinking."

While directing her peers was far more daunting, reprising Rachel still pricked those nerves.

"When you start attaching negative emotions like 'I'm an alcoholic, I hate myself', you start feeling nervous. I'd literally be giggling in scenes, so I just had to sort of summon myself, remind myself I can do this."

After that, it was like slipping into an old skin, complete with the show's best one-liners.

"I remember someone once saying Rachel says all those things you're too scared to say but you wish you could. She'll do it her way, thanks very much, and she doesn't suffer fools."

But yes, Rachel has grown up a bit. She's more work focused and less likely to jump down people's throats, Bloomfield says.

"People keep waiting for me to yell at them!"

"She's still got that defensive black humour, and she's drinking. Maybe when that subsides – or when they hook me up with someone – there'll be a little more warmth, because in a relationship someone loves you." And Rachel has her sights set firmly on Dr Love.

Shortland Street plays weeknights on TV2 at 7.