I've been watching them from the time Gina, Rose and Polya arrived at B1. It wasn't just the boob she went for. She grabbed her pussy earlier when they were in the living room and even licked it for a few seconds. When they were in Polya's room, she kept trying to pull Gina over to her but Gina kept moving away. Then later on, they mimed jerking off dicks when the four girls were in Gina's room. That and Rose kept touching herself and licking Gina off and on all night.
Rose tried literally all night. But every time she'd go for it, Gina would either pull away or start dancing again. It's clear that Gina's not into her that way.