AITA for refusing to share a bed with a relative with night terrors in order to accommodate my boyfriend?

I (25F) recently moved to a new city for work. My grandmother and I have gotten very close in the last year, especially after my mom passed away. She sold her house and moved in with me, which has been great! <br><br>She has two sisters, "Cass" (short for Cassandra, 42F) and "Lily" (27F). Lily lives on the other side of the country, so she has only visited me twice. Cass lives nearby, but has never visited me because of past resentments between her and my grandmother. You’ll see why. Both were informed ahead of time that I only have one guest bedroom, and both have complained and accused me of favoritism for not having a separate room available for each of them.<br><br>Cass has night terrors. She sleeps talks, sleep walks, and sometimes wakes up confused. Growing up, having to share a room with her was a nightmare. One night she punched me in the face and broke my nose. I’ll spare you the details, but she has hurt me more than once while asleep.<br><br>Last week, she emailed me to say that she hasn’t seen my grandmother in years and is starting to feel a little bad about it. She asked if she could visit, and I agreed. My boyfriend “Drew” (26M) has been sleeping over most nights lately, so I asked him to sleep at his place while Cass is in town. He refused, saying he has work obligations. I was annoyed, but he reluctantly agreed.<br><br>Cass arrived a few days later, and I was preparing to set up the air mattress for her when she insisted on sharing a bed with me. I refused, explaining about her night terrors, but she denied that it was still an issue. I even offered to sleep on the air mattress and give her my bed, but she got upset and accused me of treating her like I hate her. She then berated me for not having two rooms available, calling me selfish and spoiled, even though I told her multiple times ahead of time.<br><br>She then called Lily, who joined in on the berating, saying that she always felt scared of Cass and that she’s lying when she says she doesn’t have night terrors anymore. Lily, by the way, has never offered to let Cass stay with her. <br><br>Later, Drew stopped by and I told him what happened. He said that I should just let Cass sleep in my bed. I said no because if she attacks me, I will get in legal trouble. He said I’m being paranoid and that I need to learn to forgive and move on, and that I’m spoiling our relationship over petty resentments. He then said that if I really don’t want to share a bed with Cass, then I should let him sleep in the guest room. I was floored. I told him to go home, and he called me immature.<br><br>I am conflicted. Cass believes that my unwillingness to share a bed is proof that I hate her. Am I the asshole for not giving her the benefit of the doubt?