AITA for insulting my partner’s roommate because I feel she’s harming our relationship?

My Partner hast had a roommate for almost a year. At the beginning, it wasnt an issue since our relationship was pretty fresh. Over time, however, the situation has started to seriously bother me..
The roommate doesnt work, isnt looking for a Job, and doesnt seem to be actively searching for her own place either. From my perspective, she is largely living at my partners expense and has become very comfortable with that situation. I also really dislike her on a personal level, she has previously said things to my girl like "If you Cheat on him, i would be fine with it and wouldnt tell anyone". It was without any context and my girl immediatly told me this.

Because my student room is to small for the two of us, i usually stay at her place. Whenever the topic of the roommates future comes Up, it gets shut down quickly. My partner says she talks to her roommate about moving out and her plans, but it feels like the roommate just says she’ll "Take care of it" and then nothing changes. For me personally the situation started to affect our relationship more directly because my partner cancelled plans with me a few times because the roommate needed her or got involved somehow. I said very early that i accept the situation as long as it dont harm the relationship, but it feels like its going in this direction.

In a moment of frustration i called the roommate a "lazy, useless rent nomad". Since then, my partner becomes irritated and annoyed whenever i try talk about that issue so i stopped trying a few weeks now. Now im unsure whether im justified in my reaction or If im overreacting.
So AITA?

Edit: it was supposed to be a temporary solution with my Partner taking the roommate because roommate had issues with the ex, it was Not supposed to be a Long term thingy.