Am I being stupid about a girl liking another guy?

Tale as old as time I guess. I am a nervous guy and I really like this girl. The problem seems to be that she is into another guy. I don't wanna sound like I'm just jealous. What I'm struggling with is we have had some good moments. There was tension and flirting and whatnot. It felt real. It felt like it was going well until another kid in her friend group came up to us and I realized what was going on.

He's great I'm not gonna lie. we have a lot in common but I have a feeling that she likes him and he likes her as well. I don't wanna be that weird guy who is around two people who have a solid chance. But at this point, I'm friends with both of them and I don't wanna be.

I guess my real problem is how do I stop being friends with them even though our paths cross every day. I don't wanna make it weird, but I'm not going to be the guy stuck in the friend zone.

Another question I have is, do girls flirt with multiple people sometimes or was I just over thinking a situation and glamorizing something that wasn't really what I thought?