People with personality disorders, depression, suicidal tendencies can act in all sorts of ways.
Just as people without these things can do.

What isn't unusual is people trying to escape a bad situation or experience cutting ties with anything that reminds them of it or they associate with it.

Maybe she just wants to shed that bit of her life, and as you were a part of that it means letting you go too.

It doesn't mean you were used. Not all relationships are meant to last forever.
People grow, mature, change. They want different things,.
It's sounds like you did a good thing by this girl. You supported her through some tough times and gave her the support and strength to get out.

It seems part of that included letting you go as well. Doesn't make her a bad person. Just means she is looking out for herself, which is maybe what she needs,to do right now.

Perhaps you could look at ways of moving on. Forgiving her for hurting you and accepting she probably wasn't in a healthy place for a relationship.

Wishing you all the best.