Roommate secretly got a cat
My roommate secretly got a cat. She brought up wanting to get a cat a few weeks ago, but I protested saying I don't want a cat in the apartment and asked her to get one after I move out. However, today I saw her posting a story with a cat in her room. When I asked about it she said she is keeping this cat for her friend for a month. We have 11 days left on the lease. When I asked her why she got a cat without consulting me, she said she knew I would say no and she didn’t want to get my permission for it, and it was an emergency because her friend needed a cat sitter (her friend lives in a different state btw, why he had to drive to another state to leave his cat is beyond me). I pointed out it was uncool of her to bring a cat without any sort of communication with me, especailly when she knew full well I'm not a fan of keeping a pet in an apartment. She kept saying the cat will stay in her room and won't get out so I must adjust. She kept answering me in disrespectful and aggressive ways and refused to take any of my concerns seriously. I asked her to take the cat elsewhere if he/she gets out and she vaguely agreed. (Considering her character, I don't think she will hold up her end of the agreement).
And then she goes on to post another story about how I woke her up at 10 am in the morning by banging on her door. She later posted memes about how she managed to get under someone's skin and I'm pretty sure that was about me. Am I making a bigger deal out of this? How do I deal with a disrespectful roommate who has no regards for others?
Ps. Our lease doesn’t allow pets, even temporarily. I don't know how that's going to backfire if the landlord finds out.