She chose to go with them to a party at Jackson's home and at some stage during the night she and Jackson went upstairs to his bedroom.
It is alleged that McIlroy, from Royal Lodge Road in Belfast, walked in with no clothes on in the hope of joining in and that the fourth accused Mr. Harrison from Manse Road in Belfast sought to cover up what he realised had happened and tried to mislead the police enquiry that followed. One is accused of indecent exposure and the other with perverting the course of justice and withholding information.
A jury was sworn in to hear the trial yesterday and today, Toby Hedworth QC for the Public Prosecution Service (PPS) gave them an overview of the prosecution's case against the four accused men.
"Effectively, this group of friends were keen to have sexual activity with this young woman, regardless of whether or not she was prepared to do so".
The woman, who was 19 at the time and can not be named to protect her identity, was initially questioned by lead prosecution barrister Toby Hedworth QC about the events prior to her ending up in the bedroom of Mr Jackson's south Belfast home on 28 June 2016.
Mr. Hedworth said it wasn't clear who actually invited her.
Mr Jackson and Mr Olding contend the sex was consensual. Neither of the players, who have represented their country a combined 29 times, will play at club or national level until the matter is concluded, the Irish Rugby Football Union has said.
"The night ended, we say, with the first two defendants engaging in sexual activity with that young woman against her wishes, as they well knew or as they simply were not interested in considering".
'It involves a young woman going to an after-party with other females at the home of a well-known sportsman, Patrick Jackson, the first defendant. He added she did "not suggest that she attempted to fight him off" but she described herself as "being numb throughout what happened as if she herself was not there". It is alleged Mr Jackson had sex with the alleged victim in his bedroom.
The complainant said Mr McIlroy said to her, "You f***ed those guys, why not me?", to which she replied, "How many times does it take for a girl to say no before it sinks in".
Later, the woman told the court: "It's not OK".
In a text message to a friend the following day, the woman said she had been "raped by three Ulster rugby scum". The complainant said that Jackson asked her did she want to "join in".
At 11.17am Mr. Olding texts: "we are all top shaggers" and adds "there was a bit of spit roasting going on last night fellas".
Paddy Jackson (left) and Stuart Olding (right) arrive at Belfast Crown Court this week.
He said the complainant had consensual oral sex with him and also with Olding.