She had dropped her daughter off at the Kergunyah property between 6 and 7pm on the night of September 2, 2017, and planned to pick her up again the next morning after she stayed there the night in a swag with another friend.

Instead, she received a call from police officers at Wodonga at 5am.

The alleged victim had gone back to her friend's place a few hours earlier with her friend's mum, who drove her to see police.

The next step was to travel to Melbourne to be examined by a consultant pediatrician.

By the time she got back home with her mother it was late, so they waited until the next morning - on September 4 - to talk about what the girl said happened.

"She was having a good time at the party, then she met these two boys," the mother said.

"One of them kissed her and she kissed him back."

The mother told the jury at Wodonga County Court on Monday that her daughter said she was walking behind Mitchell Bowran then Charlie Star came out of the portaloos.

"Somehow they ended up behind the shed and that's when they raped her," she said.

"They took turns pulling her pants down and raping her.

"After it was done, they just left her."

She said the girl was still very upset and tired when talking about the ordeal.

The host of the party, who had been celebrating her 18th birthday on the night, told police at the time the alleged victim was wearing a black mesh top with a red bra underneath.

"I know there were a few comments about what (she) was wearing and doing … She seemed her normal self which was happy, flirtatious, bubbly," she said.

"I noticed (the alleged victim) was dancing with Mitch, she was all over him."

Speaking under cross-examination from Star's barrister Charles Morgan, she said she shone a mobile phone light behind the shed and saw the victim sitting and Bowran standing a metre away from her, both laughing.

"It was a private moment between two happy people behind the shed, isn't that right?" he said.

She agreed, saying she did not notice anything unusual occur at the party after that point.

Both Mitchell Bowran and Charlie Star had been told not to attend the 18th birthday party held in Kergunyah in 2017, where they would later be accused of raping a teenage girl.

The birthday girl had invited about 70 friends to the party, held on her parents' rural property on September 2, sending the invites out via Facebook.

Bowran and Star, both 20 at the time, were a couple of years older and had not been invited.

But they still asked if they could come to the party, getting in contact via Snapchat and Facebook Messenger respectively.

The party host told them both "no".

She explained to Wodonga County Court on Monday that she did not want older people there who were more than the age of her brother.

"I didn't think they were bad guys, I just didn't have anything to do with them," she told police at the time.

They arrived anyway with a third young man who had also not been invited.

"They came up to me and wished me a happy birthday," the teenager told the court.

"I didn't speak to them after that."

The alleged victim, a 17-year-old, also had not been invited to the party originally, but was told it was OK to come when she asked permission from the host.

She said the alleged victim had not been a close friend.

Asked by Star's barrister Charles Morgan if she belonged to the "cooler" group at school, or what he called the "top dogs", she answered "yes".

Bowran and Star have both denied the allegations of rape, saying the sexual encounter was consensual.

The trial in front of Judge Richard Smith continues on Tuesday.

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