I think you should fuck her, his sister, his mother, his grandmother and finally him too. YOLO
p.s. - I've recently got quite some attention from one cute girl. Found out she has been in LTR for a few years. She knew I have a gf too. I played it calm, did not cross the line, but it was obvious that she's ready to try something else (maybe first serious bf or some shit). Haven't seen her in a while, and today found out he has proposed to her. I wonder how big the chances are they won't end up in divorce, given a fact that she was clearly sending the signs..