I dunno what to do about this person

Ok so I was friends with this girl (we’ll call her B) for like 5 years. I grew up kinda sheltered so I didn’t know what toxic people were like, and looking back it‘s pretty clear this friendship was. It ended about two months ago. She has since gotten on medication and has seemingly gotten nicer. She and I don’t really talk at all, I only see her at church, but we used to avoid each other like the plague cause neither of us wanted to interact. But now she’s been getting closer with my younger brothers (they are kids she is a teen) and I’m pretty sure is gonna try to rekindle things with me. I’m not really sure what to do. One part of me is like “she’s changed, you can trust her again.” And the other part is like “girl she has pretended to be changed before who says this isn’t the same thing?” So yeah, if you need more context on what happened I can give it, but y’all I need some help With this.