She talks bad about the 'bad' friends?
what does she say about them?
Who does she spend more time with?
Are you one of her friends?
It's funny how life works sometimes. Sometimes the people who treat us the worst are the ones we think we need to prove something to. If someone cares about you unconditionally, then you don't have to prove anything or do anything to make them like you. However, when we have people that don't treat us as well as we think we should be treated, then we tend to strive to prove a point, to get them to like us and it can sometimes become an obsession.
Alternatively, you can have someone who's self esteem is so low that they believe that they somehow deserve to be treated this way. This can be totally subconscious and they may not even realize that they're doing it.
I welcome your thoughts, let me know if you want to talk more
I completely understand what you're saying, and again, sometimes it's the people who treat us the worst that make the most of an impression on and that we feel like we need to prove something to or make an impression on. It's as if they are never happy with us, so we try to please them. It's not necessarily a 'mental illness' but certainly a part of our psyche, something that may have happened where someone she really loved treated her badly and she started to equate this type of behavior with love.