Update with context

I last wrote about a month ago what I should do because I was really confused between 3 girls, but now I'm lost because the one I actually liked is trying to flirt with me and Im talking to some girl I talked to before. For context I'll put a screenshot of the last post.

A week into 2024 a girl who I used to be really close with messaged be apologizing for what happened with her 7 months before. I wasn't blocked, but we cut talking to each other. Now for the past 2 weeks we've been talking everyday. It's important to mention she believes she might be bipolar, and this doesn't help because now I'm not sure if she wants to start a relationship. This weekend I think she was going through something and she was putting on her notes "I'm completely happy with how everything is right now, no changes needed" or something along those lines. During that time we talked less and it felt more forced, now it doesn't as much. I'm back in her friend group and everyone seems happy that I'm there. They invited me to party I'm supposed to go to. Now I'm confused because of the other girl.

After going back to school from break I was able to move seats and the girl who I liked in the first post came and sat next to me. Now I'm pretty sure she's trying to flirt with me (I'm not entirely sure but yes). I don't know if she's the type of person who dates every few weeks/months or cheats. I still am attracted to her but I'm not sure if I should act on it.

I still don't know much about her just her music taste. I think I'm attending to her because of the music and her looks so far but I'm not 100%. The first girl I actually know her personally and I like her for looks and personality (we connected on a lot of thing like music, movies, hobbies, etc).

Should I talk to the second girl? Because I don't know if the first girl wants to be in a relationship

If it's confusing or more context is needed please let me know, again thank you.