I'm upset at my girlfriend when she restates whatever I say as a question
Do you believe that she's aware that she's doing this to you?
Yes she does it on purpose
You should tell her you find it annoying. If it continues you should be able to leave the relationship and not be forced to stay.
I don't want to hurt her feelings. She can keep doing that.
I don't think you would hurt her feelings if she is doing it on purpose, it sounds like an actual conversation that needs to be had. You'll be less happy than you could be if you stay quiet, and is that a life that you want to live?