Welcome, phoebenna!

I just wanted to pop in and join
Mutt in welcoming you to the discussion forums. Mostly we are here because someone in our lives has behaviors that are characteristic of BPD. They haven't all been diagnosed with BPD, but it's the behaviors, and how we deal with them, that is important. You will see from reading the posts here that you are far from alone.
Thank you for sharing what you have thus far:
I'm constantly stuck in the middle of her dad and stepdad.
It sounds like you have really had a tough time, and I'm sorry for that. One thing that can really help with allaying some worry and frustration is understanding. And, it sounds like you are willing to understand your child better, and that is pure love, in my opinion. Luckily, you've found our website which can help you in that regard in spades. When you're ready, just start reading the site articles and do the Tools and Lessons located in the right panel of this page. The other thing that you'll find here is support for
yourself.
I do agree with
Mutt that you are possibly caught in a Karpman Drama Triangle.
You will find a lot of people here to talk to, who will provide you with support and some good advice. Keep posting - it is very therapeutic, and you will be greeted by so many people with circumstances similar to your own. You will be amazed. Take care of yourself.
Keep writing, keep processing, keep learning!
-Speck