I don't want to let my girlfriend sleep over
Do you have a reason to keep her away?
I hate the thought of other people sleeping in my bed.
If you are both together you should sleep in the same place from time to time. It's weird to not want her to stay over.
That's a stupid perspective. I can't sleep if she is there.
I can understand that sometimes it is hard to share a bed with another person if you are not used to it. Depending on your age you shouldn't sleep with another person just yet. If you are not ready it is okay just let her know.