This girl and I have known each other for a decent chunk of time, around 3-4 years. Shortly after we met we tried dating, but it ended up becoming a LDR and with us both being young and in high school, it ended pretty quickly. Given that the breakup wasn't anything to do with either of us really, she's still one of my best friends till this day. Recently she's been having guy trouble and ended two relationships in the span of two months. During this I console her and be a good friend. After a bit of time, she confesses she's starting to have a crush on me again. Admittedly, I do still think about us and am curious about what could've been. A little while after this happens she upgrades one of her FWBs to a boyfriend. She's still in a relationship with this guy right now, but soon I'm visiting her and we've talked about what could've been and she admits that something could happen given the right conditions. She even mentioned to her boyfriend the entire situation and she claims he stated only that "If anything happens let me know." My question is, what role should I play in all of this? Am I a rebound? Am I a bad person if I let anything happen between us? The fact that this will all be happening soon sends me reeling. I'm hoping to figure this all out before I visit.