Why do I always end befriending maniplitive people? How do I see through them?

My old house mate (we kicked her out finally)had been using mine & my other house mate's mental health against us. She's stolen a few hundred pounds off us and had been playing mind games. She's still using mind games. We had been sending her post to her mothers house (the only known address we have of her) so she wouldn't miss her letters. She's threatening to tell the police that we are "harassing" her unwell mother.

my other house mate and I are considering getting the police involved. I'm now too scared to leave the house in case I bump into her. We've changed the locks but I'm still scared she's still there. In the past she's poisoned her previous house mates.

shes not the only manipulative friend I have had. There's been a lot more in the passed. When i was 13 I was groomed by a paedophile

why am u so stupid? Why do I always fall into people's trap?