A trial about two blondes fighting over who looked better in a silver dress has been resolved - just in time for the 21st birthday party of one of the women.

Bridget Masters, 20, was yesterday acquitted by a Wellington District Court jury of wounding with intent to injure after smashing a champagne glass on the head of her ex-boyfriend's new 22-year-old woman.

At the centre of the altercation in the toilets of the Wellington bar Temperance was a silver dress - bought in the United States and brought back for Ms Masters.

But she rejected the dress when she broke up with her boyfriend of 18 months, and it was still in his wardrobe four weeks later.

The man's new girlfriend, Victoria Clapham, saw the dress as they prepared to go out on a Friday night, and he gave it to her.

The man, Matthew Vibert, took Ms Clapham to the bar, where he knew Ms Masters would be.

She was photographing VIPs for a website to take her closer to her dream of becoming a television presenter.

At 2.30am, the two women clashed. Ms Masters yelled, "Why are you wearing my dress?"

Ms Clapham allegedly responded, "Because Matt gave it to me and it looks so much better on me than it does on you."

Ms Masters' mother, Tracey, said after the verdict that it was unfair her daughter had been dragged through the courts for almost a year.

Ms Masters had not been allowed to drink during that time.

"It's been really hard on her, when actually it wasn't even the drinking."

Ms Masters said outside the court yesterday that she would celebrate her acquittal with her family. She turns 21 next week.

"I kind of feel like I'm in heaven right now," she said. "I was the victim of this whole incident."

The jury saw diagrams of the alleged crime scene, with arrows marking distances between sinks and toilet stalls and possible trajectories of cocktails.

The case depended less on the women's blonde hair, drenched with alcohol and blood, than on the angles and speeds at which the two bent their elbows and flicked their wrists to splash cocktails at each other.

Did Ms Clapham extend her right arm in a twisting motion at shoulder height as she flung her drink, or was it a light flick from near her chest?

The jury members were asked to consider several other questions.

Could Ms Masters really have forgotten that she was holding her champagne glass, which smashed into her adversary's head, when seconds earlier she had flung its contents at the silver dress?

The difficulties were compounded by evidence from five highly inconsistent witness accounts.

The most "balanced, reasonable and accurate" witness, according to the prosecution, had consumed only five vodkas and, in her own words, felt "pretty fine".

A sober bar employee who was walking past the doorway claimed to have seen Ms Masters walk three strides towards Ms Clapham in a space as cramped as a witness box.

Ms Masters and a friend, who had been next to her in the bathroom, gave consistent accounts, but the prosecution suggested they could have arranged to tell the same story.

The friend said they had not had time to collude because they were too quickly whisked out by bouncers to police, and "I was crying, she was crying".

Among the contested facts were whether Ms Clapham had screamed at Ms Masters: "I'm going to f***ing smash your head in, f***ing bitch."

The court also heard that the bleeding blonde was aided by a brunette, who tried to wipe away the blood with toilet paper.

Ms Clapham allegedly stopped her, saying, "Just leave it. I want the police to see how it is."

The agreed facts were that Ms Masters first yelled at Ms Clapham, then splashed the dress with "bubbly".

Ms Clapham responded with a splash of her own - "the return act", as Judge Andrew Becroft called it. Then Ms Masters allegedly smashed her glass into Ms Clapham's head.

Crown prosecutor Jojo Murdoch argued against self-defence.

"The accused was not hit by a glass or a punch, she was hit by liquid," she told the jury.

Defence lawyer Mike Antunovic asked the jury, "What can you really be sure about?"

Ms Masters was watery-eyed as she entered the courtroom, sitting in the witness box with tissues.

She broke down at Mr Antunovic's defence.

"Your judgment will affect this young woman long after we've packed up our bags and gone home for the weekend," he told the jury.

After her acquittal, Ms Masters was overwhelmed with emotion and mistakenly walked back into custody.

She had about 10 family and friends supporting her.

The complainant, Ms Clapham, had already left town.