Unstable room mate

From experience with previous relationships.. With Giant, Dane, Cord, among others.. When I start to write a lot of posts about them in a short amount of time, things typically aren't going very well. I typically don't have a need to write, if things are going well. 

So with that in mind, here's another post about Elle. The really frustrating part is: We, the two of us, are fine. At least as fine as two people learning to get to know each other can be, early on in a relationship. Cord and I ended in our first fight. Elle and I got through that part just fine, and I feel like we're communicating well enough. The problem isn't her, really. It's her room mate. 

Another trans woman, Elle has known her for over ten years. They've been sexual partners on and off for about as long, but not romantic partners. Elle is very clear (to me..) that she doesn't consider the room mate a partner on equal grounds with me and her girlfriend. And yet.. It's clear the room mate has a different idea. They've lived together for a month now, and there's been no end to the problems that room mate has caused. Every week, there's something new.

The room mate's really unpredictable, with wild mood swings and a very relative relationship with the truth. She's the kind of person who hears what she wants to hear, who remember the parts she wants to remember, and refuses to acknowledge a different perspective. She's controlling, manipulative, and mentally unstable. One moment she's screaming at me and threatening to call the police, less than 20 minutes later she's smiling, laughing and hugging me. The fact that she's also using drugs regularly doesn't help the overall impression, but I don't think she'd be any more stable if she'd been clean either.  I don't feel safe with her around.

The problem is that Elle isn't standing up to her. She's very clear, to me, that she doesn't want the room mate as an equal partner to me and her girlfriend. Yet she's willing to go along with it, to keep the peace. Even when that "peace keeping" means that both me and her girlfriend are worse off. 

I've started advocating for Elle to move out of there, get something for just herself. There isn't much on the market in her price range, but it's possible. It feels like a big step, when I haven't been with her for three months yet, to encourage her to move away from her room mate... But if she doesn't, I worry what it will do to us as a couple. I'm not sure I'm able to keep hanging out in a place that I find fundamentally unsafe.