I don't think the problem with her using the Force is the problem, per se. If she was a nobody with zero training, we could say she was able to reach out and use it for something (as Chirrut being an example up thread). I think the problem with Rey, overall, is that it's stated she's strong in the Force (cliche perhaps, but fits the setting like a glove). In the same movie, we see her being (relatively speaking) somewhat capable of using mind trick - and more so, she seems to get good with it in the same movie. And up to this point, in so far as we know (and TLJ seemed to confirm*) that she has no training, no idea of the Force, or Jedi ways, or anything really.
*TLJ didn't give us any details of her getting any kind of training, and I'd assume if she was a student of Luke's he would have known about her. Also the assumption is he's really the only teacher around at this time, since there is nothing to the contrary.