More than the dress, the speeches, the mother of the bride, the band or even the groom, bridesmaids can make or break a bride's special day.

A maid from hell can make the blushing bride go pink for all the wrong reasons and turn that dream wedding into a nightmare.

The select few friends chosen to take on the honour of maid duty carry a heavy burden, and bearing that burden in mind, is it any surprise it's prone to going so terribly wrong?

Just last weekend, an Australian bridesmaid at a wedding in Huia had a few too many tipples and ended up at the centre of a search and rescue mission in the Waitakere Ranges.

The dazed maid - who had allegedly drunk two bottles of spirits - wandered into the bush in the early hours of Sunday morning, trying to find her way home. After several hours searching, with the aid of a dog and a helicopter, police found her curled up asleep about 15m from the roadside.

But that pales in comparison to some behaviour Shirley-Ann McCrystal, a wedding consultant and celebrant based near Taupo, has seen.

The worst case was the maid who slept with the groom on his stag night. "The bride found out about two days before the wedding. There were a few tantrums and no one was talking to each other at the rehearsal the day she found out, but the wedding still went ahead," says McCrystal. The guilty bridesmaid carried on with her duties but "there were a lot of dark looks", she says. "The bride must have been a very forgiving girl."

Another bridesmaid - the best friend of the bride - threw a wobbly on the wedding day and pulled out, says McCrystal. "That left her without her chief bridesmaid and because this girl was very large, there was no way anyone else could fit her dress."

But McCrystal insists the vast majority of bridesmaids she has met have been "very sweet and helpful".

Auckland celebrant Peta Hardley agrees but, like McCrystal, has also encountered the odd bad egg. One ceremony was held up by a drunken maid throwing up in the toilet.

"Some bridesmaids make it all about them instead of about the bride," says Hardley. "It's, 'Oh my gosh, I've put on so much weight and the dress won't fit', or, 'Oh no, I've got the wrong shade of red on my toenails'. It's so the focus stays on them instead of the bride."

She has also seen brides so fed up with their maids' antics they've fired them. "I've had brides change bridesmaids the week prior to the wedding, which has caused a few headaches," she says.

Auckland psychologist Teresa Ash says responsibility can bring on out-of-character behaviour. "Wedding preparation can take a lot out of people. Frictions and tensions can build up, there might be a bit of passive aggression and alcohol brings these things to the fore."

Weddings can signal relationship change between the maid and bride. "If her life is changing rapidly, these things that exist in the subconscious can come out," says Ash.

Christchurch-based psychologist Dr Alice Boyes agrees. "Someone might not be used to their friend telling them what to do, like what dress to wear, and struggle to cope with that disruption."

Bad bridesmaid behaviour can also be a sign she's not happy to be there. "In some cases there's a conflict between wanting to support the bride, but not thinking the marriage is a good idea," says Boyes.