Don't roll your eyes at her; she didn't realize the force was real! She thought Luke Skywalker was a myth! And this is ... pretty mind-blowing. Since discovering she's force-sensitive, she assumed that this was something that had been latent inside her. Something that she's lived without her entire life, something that she could continue living without. The idea that she's actually been unconsciously making use of it her entire life changes everything.

"But I thought you had to train for years," she says. Never mind the fact that she managed to use the jedi mind trick on that stormtrooper without any training whatsoever.