@NineTails I thought that for a second too, but I think it's something that happened when his brother (who she thinks is him) was first adopted by her family. He didn't like her initially because she was one of them I think. That's why she's covering it up so he doesn't see it and act disgusted. She doesn't want to see the same look on his face as back then. She remembered it recently. That or he acted like that in one of the previous chapters where he shrunk to kid form from overusing his powers. I can't totally tell from that little flashback image, but I'm leaning towards the childhood thing.