Does girl 1 have a bf just now?
It might help if you think about what attracted you to each girl in the first place.
You say that you started falling for 2 after
you found out 1 had a bf.
Do you think your feelings for girl 2 have anything to do with the fact that she was available, whereas, girl 1 was/is in a relationship? You dont have to answer that here, but you need to be honest with yourself.
Anyway, I hope you get things sorted out!