Am I over reacting on their friendship?
Why is she leaving her belongings here?
She is a great person, she doesn’t yell or scream or get violent. She occasionally self harmed.
Hey Marty and thanks for posting! Welcome to the site!
Are you overreacting? Only you can answer that by flipping this situation around. Let's say you're in a pretty good relationship but there's something you don't get from it- and it can be anything. Let's say your favorite hobby, she hates it and you love it. But your best friend also loves your hobby so you hang out with him/her often. Not too much, maybe a few hours a week...but it does take you away from home during those times and your spouse is irked by it.
Your spouse demands that you give up the hobby and give up the friend, it's too harmful to the relationship. Is that a reasonable ask?
For your girlfriend, she gets something from that relationship that she doesn't get from you. And you might feel a touch of jealousy over that, but it's probably something emotional we get from different types of people in our lives. Maybe she's more comfortable talking to him about certain things...or maybe he needs her advice for his own problems. For instance, I'd talk to my mom about relationships and talk to my dad about work. It's not that the other parent couldn't have meaningful advice on everything, that's just how we do it as humans.
Then there's my best friend from childhood knows things about me that I've never told anyone else. Why? I don't know why, it's not like I'm carrying deep, dark secrets. But I know I can tell him anything without judgement, and that's worth its weight in gold.
So again, this comes back to you. Were you wrong to demand that she stop talking to her friend?
For the other question, why won't she pick up her stuff, there could be a million answers there. I have no idea. In my BPD wife's case when we separated, she didn't want to come over and pack the stuff up, it was too emotional for her. So eventually I did it for her.