My mom finally got a room where she wanted to go after rehab. She is really nervous about sharing a room. Things like the bathroom, noise and being able to look out a window. I feel so bad for her. I'm sure everything will work out, but she knows this will be the last place she'll live at and is a very quiet person.
My MIL had a few different roommates while in LTC. One was in the latter stages of ALZ and basically non-responsive. Another was there due to physical impairment from a stroke and although cognitively very good, spent very little time in the room. It's not going to be like college, and a good admin team will work with your mom within reason. If she's the first one in the room she'll get the pick of being closer to the window. When the roommate's LOs visit, they will hopefully be respectful.
If your mom has good memory and cognition, you can call her every day to ask how the roommate situation is going. Keep a journal of her impressions for the first few weeks. I hope it goes well!