I really thought it was better explained in the book. She tearfully talks about what she's done and why, and says she'll track her parents down if they survive. In the movie, you hear her mom say something about Australia, and then Hermione wipes their memories and leaves. If you haven't read the book, Harry comes off more favorably, because it's clear the Dursleys are going into hiding, while Hermione seems to be leaving her parents alone and unaware.