Plot hole: The only reason the movie takes place is because the news station that Mrs. Mott watches names Claire as the woman who filled the lawsuit against Mr. Mott. It is completely illegal for broadcasters to name or show a picture of a sexually assaulted victim.
Plot hole: When Peyton is raging in the bathroom, she's making an extreme racket yet no-one hears a thing.






Answer: The same way any common criminal gets in to a house, she "broke" in by either kicking the door, or smashing a window, etc. A locked door is not that hard an obstacle to overcome.
Jazetopher