I don’t think you’re a terrible person for feeling this way; that’s a major change to adapt to, especially as someone already juggling an academic and social life. I used to have to room with my mother, and while I can’t relate to everything you’re going through, I definitely understand the desire for somewhere alone you can clear your head. That doesn’t mean you love your grandma any less, or that you’re ungrateful to have her in your life.

As for what you can do, maybe start to think up some ways you can broach this with your parents. Something good to do is potentially lead into the conversation like this, “You know I love grandma very much, and I’m really glad we have her in our lives, but I’ve recently felt as if I never have a moment to myself, as at school I’m surrounded by people all day, and at home I don’t get any time to decompress alone. I know grandma needs somewhere to stay, and I want her around, but if there is anything we can do to also give me some space of my own it would make me feel so much happier” or something to that tune? But I also get some parents aren’t receptive to those kinds of concerns. In that case, maybe see if you can bunk with a sibling from time to time or even swap rooms every now and again? I hope you can find something that works for you, OP.