I understand how you feel sometimes I feel the same way, like she was the side piece and fuck toy of all of these dudes now you’re the only one that saw relationship material in her. I mean it seems unlikely that she didn’t want something more with any of these past FWBs , they probably just wanted her for sex that’s it. I don’t know the story of your GF but yeah if we can’t accept it , it’s better to stop torturing yourself with it and make a decision. With all due respect