Her experience is most symptomatic of an obsessive compulsive disorder, or OCD.
Maxine suffers from OCD which is making her repeatedly do the same thing until it is perfected. In this case, she is constantly dwelling on the fact whether or not she locked her door, and she won't feel at ease until she finds out for sure. However, even when she checks again, some time after that she may start feeling anxious again and start wondering if she locked the door.
