Agree With SnakeCharmer on everything. She's 13 yrs old and been through 2 divorces so far, with you being the third SO your bf has had. So I am not judging him for having broken relationships but pointing out that for a 13 yr old or any kid for that matter it brings with it a lot of uncertainty and insecurity. What our kids need are to know that they are loved, cared for and get the attention they need and the divorces in her life has placed her squarely in the middle of confusion and insecurity. Yes, she is acting out, and no, I don't think it's right for her to do what she's doing but packing her things and sending her away... that, personally really worries me that you would even consider that.

A child is not a property or garbage to be put out to the curb when they're less than perfect for us. Besides the fact that its NOT YOUR PLACE to say whether she's sent away or not. She's not even really a step daughter at all. She's your boyfriend's daughter and even less you have any say in the matter.

She's being manipulative and probably mean and nasty, I believe that. But like SnakeCharmer said you need to be the adult here.

Being a non parent in a situation like this is never an easy thing to do and the non-parent, whether a step or a gf/bf it doesn't matter, the bond with the child is never automatic and I know. I made a lot of mistakes with my (now ex) stepson. Trust me, look at her as a 13 yr old that is floundering, trying to find her place in the family, being 13 she's already struggling to find her identity and on top of that dealing with a gf of her dad's that's not her mother.. has a mother and an ex step mom. Try to understand, she needs security and love, not your criticism and anger.