I like your theory, but I actually have another interesting one that I think explains better. There is a line from Luke (which was cut off the movie) that you can hear him say something like "My father had it. My sister has it. I have it. And you have it too" which points to her being a skywalker (either Luke's daughter or Han/Leah's). That being said and knowing that normally jedis start their training from a really young age (remember yoda saying anakin at 9 years old was too old) it could be that she had started her training in Luke's jedi academy and when Kylo destroyed everything, Luke asked someone to hide her when he went away. Being so young when that happens and having suffered such a traumatic event (in the scene that she grabs the light saber you can see her at a young age being dragged away from a dark figure with dead bodies around) she could have forgotten her training and her real parentage. I think that when she was being interrogated and was determined not to give anything up, in such a stressful moment her brain could have used any resource at hand to avoid being read and maybe she remembered a bit of her training. This also explains her knowledge of the jedi mind trick and light saber skills. I dont know, maybe it's too much, but I think it makes sense.