The woman had been at a nightclub in Belfast with a group of friends where they met Ulster players in the VIP section.
Belfast Crown Court heard the alleged victim went back to the property with three other young women, who she did not know personally but who were mutual friends of a close pal.
Fly-half Jackson, 26, and centre Olding, 24, deny rape.
Yesterday they stood in the dock alongside two of Jackson’s friends, Blane McIlroy, 26, and Rory Harrison, 25. McIlroy denies one count of exposure while Harrison denies perverting the course of justice and withholding information.
Olding, who has four caps, allegedly wrote on messaging service WhatsApp: “We are all top shaggers” and “There was a bit of spit roasting going on last night fellas”.
It is alleged that 25-cap Jackson replied on the same phone app: “There was a lot of spit.”
The trial, expected to last five weeks, continues.