There are two separate issues here. The first one being that he lied to you. I’m sure you know that that is a red flag. And if this girl doesn’t continue to become more and more faded into the background, this problem will follow you around. I experienced something similar. My bf and i’s mutual friend, he liked her for awhile. She rejected him. We started dating..and suddenly she wanted him. Of course right? But he did the right thing, he made our relationship and his commitment to me extremely obvious, he maintained his friendship with her at a healthy distance. Now, four years later, we all hang out in group settings all the time and it’s long forgotten about. But that was due to his actions and commitment and I knew I deserved no less, and so do you. So that Brings me to the second issue. Our mutual friend made me feel the same way. Although kinda the opposite lol. She was loud, fun, extremely likeable, and super into tons of sporty and nerdy things like him. Meanwhile I’m shy, super girly interests, sensitive...it was really hard for me to accept that he would choose me when she was right there. But guess what? I had to. It ate away at me for like, two years. Now here we are four years in and I wish I hadn’t wasted those two years feeling insecure. There’s always gonna be someone in the room more good looking than us. There will always be someone skinnier. Someone more charming in the room. Always. We have to accept that. I think we place extremely high standards on ourselves. And if someone seems slightly “better” than us, as in better in some BS way society has made up e.g. “low maintenance”, then suddenly we are trash. Which isn’t true at all. If you’re going to get through this you’re going to have to understand and see what HE sees in you. But this is a two way street. He will need to make that obvious, and he will need to make his commitment very obvious to her as well.