Need help

I really don’t know what should I do? I am talking to a girl more than 1 month and now I have developed some feelings for her. But what’s happening now is that someone she used to love alot and still love, came back, after he left her and now she couldn’t control herself talking to him.

That person is a toxic person and only wants to use her and she knows that. She daily cries because she can’t have him love her back.

After she met me she realised that I am the best person she ever met, but she doesn’t know why she can’t love me.

I’m being treated as a second choice, and it hurts alot. But when I tell her to leave me she just can’t, she doesn’t let me go because she wants me to stay in her life as well because she thinks that maybe something could happen in the future.

She isn’t in relationship with anyone but I am not sure what should I do in this situation, it is very complicated now.