On a hot day in London the former Mrs Depp sat down in the witness box and started by swigging from a bottle of water. By lunchtime she was on her third bottle. In the afternoon she got through at least another three.
You can't say these Hollywood stars are ever – unlike bedsheets hurriedly bundled into a boil wash – knowingly underhydrated.
It became clear very quickly that she is a certain type of woman. A luminous blonde. Beautiful, spirited, fuelled by a high-octane belief that she is always in the right. Someone not to be messed with, someone determined to prevail. In short, as far as many men are concerned, your basic nightmare.
In Court 13, she finally got the chance to tell her side of the story. After a week of evidence from her ex-husband Johnny Depp, this was her moment. Whatever happened next, Amber would be heard.
"Are you telling the court the truth?" asked Depp's representative, Eleanor Laws QC, at one point. 'Yes, ma'am,' she replied, as clear as a Texan belle.
Her testimony ranged over the distressingly short period of the couple's relationship and marriage. From first kiss to last quarrel, it was barely a blip in the space-time continuum: A simple pair of stars, two balls of boiling gas, who burned out long before their time. A lot happened, but Heard's memory was not always constant.
"It was the afternoon, not the morning," she would say crisply of one incident, but remain hazy about others. Still, it was an improvement on Depp, who could barely recall what he had for breakfast. There was talk of bruises on Amber's face that appeared and magically disappeared, like clouds. "But if I was out in LA I would be wearing make-up," she said, not unreasonably.
Speaking of which, yesterday she was a vision. Expertly applied highlighter flared along her cheekbones, while one could only admire the faultless curve of her Hollywood jawline. At one stage she took a moment to apply some red lip gloss with a wand, check it in a tiny mirror, then blot it with the back of her hand. Heard was ready for her close-up at all times.
Some think that actresses (and actors!) cannot resist the temptation to ham it up in public, and the cool 34-year-old did nothing to disabuse anyone of that fond notion. Her repertoire ranged between cheerful politesse to injured innocence to – a favourite – long-suffering victim. There was the occasional grimace or a rare quiver of lip.
Yet Heard would often look up to the public gallery and smile with amusement and warmth, presumably at sister Whitney and/or partner Bianca Butti. Once she made the sign of the horns with her hand, now and again she produced the tiniest of eye rolls that seemed to say: "Can you believe this garbage?"
Indeed. In the morning she had been ushered into court with a supporting arm by her female lawyer Jennifer Robinson, a gesture that seemed to semaphore victim status – make way for the wounded woman.
Over the past week in the UK, a lot of high-profile feminists have made their support clear for Heard, despite the fact that the three-week trial is far from over.
The Australian author Kathy Lette had a dinner for her at the weekend. Lovely. A whiff of any troubled Leftie global-celebrity female humanitarian activist in town and Kathy's got the prawns on the barbie. Baroness Helena Kennedy (another invitee) can bring along the summer pudding and make a point of order.
Cherie Booth QC and Jess Phillips MP have also shown their support, even if it has yet to be ascertained who is telling the truth.
Back in the witness box, I liked Heard's look. If she were a dress pattern, she would have been called Big Day In Court or perhaps even Amish Accents.
She wore a pleated cream blouse, a long black skirt and discreet gold jewellery to deliver testimony that was as neatly tailored as a row of pin-tucked ducks.
Her hair was tied into a demure fishtail plait, just like Elsa's in the fem-baby Disney cartoon Frozen.
Be the good girl you always have to be? There was certainly an element of that. She certainly wasn't going to let it go any time soon.
In her evidence, she talked of how the alleged abuse in her marriage was hidden at first. Of how she loved Johnny but was terrified of the 'monster' he could become under the influence of drugs and drink. It was a sobering vision.
Amber smiled a lot even though she never missed an opportunity, not once, to load up her splatter gun and fire another custard pie in Depp's direction.
It felt like a misery stream-of-consciousness, a litany of woe upon woe.
"I had very little decision-making power in that relationship," she would say.
We heard that he had a hard time asserting himself, didn't want to be the bad guy, had problems with feelings, was particularly abusive, extremely jealous, extremely insecure and ...
"Could you go a little bit slower, please," cried the judge, Mr Justice Nicol. However, Amber was not above admitting that she had her faults, too. "I also," she said, pausing to put her hand on her heart and gaze heavenwards in a manner that may well become known as Markle-lite, "have moments when I, too, felt jealous."
The case continues.