✔ 最佳答案
Why don't you like her BF sleeping over? Are they loud? Is he messy? Does he sit in your favorite chair? Or is it that you might just be a little jealous?
Regardless of the reason, I think it's only fair that if the BF is going to be sleeping there every night that he contribute to the rent / mortgage...or your friend should be paying 2/3. I'm sure he's eating, watching TV, and using water while he's there. Why wouldn't he help contribute to the expenses then?
If you approach your housemate with that reasoning, she may take the hint, or even move out. If not, there's really not much action you can take other than moving out yourself. But, I think you really need to look at why you find this "really annoying". The problem may not be entirely with your housemate.