I KNOW i can close with this girl i just don't know how. ok heres the story

this girl has a boyfriend who all her best friends absolutely HATE. and she even hates being with him sometimes and its kinda bad, thats mainly why i dont feel bad whatsoever about this. anyway, so i came to athens to party with a good friend of mine (she is the girl in question's roommate). we went to the bars and this girl and her bf were in a fight and so one of her other roommates told her, directly in front of me, to hook up with me if she wanted to get her mind of her dick bf...lol. i just played it off like of course i would do that, and just kinda talked to her and made sure to touch her a lot and shit. she loved it, and shit and she's pretty shy (or has low self esteem which would explain the douche bf) but i was still grabbing her ass when no one was looking and shit. she would just ignore it or smile and playfully push my hand away like im doing something taboo haha. anyway, in the end of the night she still went back to her bf, who like came up to her and apologized and shit.

how would you guys have handled this? should i have escalated harder? shes coming tubing with me and a group of friends, s her bf wont be there so maybe i can try then? it just pisses me off that i couldn't get her attracted to me enough to the point where she absolutely wanted me, even though i knew she was at least a little interested. what would you guys have done, or what would you guys do while tubing? i can't isolate her at all while tubing btw