Despite hating what she was doing, aiding and embedding organized crime could get her put away for life or sentenced to death, it wasn't healthy for her to spend all of her time around No-Maj's and forget her magical background completely. Hermione had been allowing her magic to build up, without any form of release for quite some time now. It was damaging, and before she had married Silas she often expelled her magic, apparating away into New Jersey.