It's all anyone's guess right now, and who knows what the history of Rey is, but you are assuming she hasn't had any training at all. What if Luke partially trained her when she was young, but had to be hidden and had her mind force wiped for her protection? What if this whole series of events, and Ren toying with her mind, awoke her force skills? I'm not digging/buying the whole she learned how to do everything from reading Ren's mind.

