just straight up say, “I’m not trying to seem uptight or anything but do you think you could try to keep it down after 10:30. I have an early class tomorrow.” (OR something along those lines) then be asleep before she starts her call, and if she does it, make a scene of her waking you up. stare at her hardcore so she gets the memo and shuts up. don’t be worried to seem a little rude, asking her to be quiet is a reasonable request as a roomate
So I had the same problem for the first couple weeks and basically told her that she needs to wear headphones and leave the room if she wants to be on the phone at a late time. We had a conversation on times it was OK and times that it was not and now anytime that she’s on the phone she leaves and goes to the common area or a study room.