When Michelle is lying in bed with Ronald sitting next to her and asking what happened, she asks him to leave and turns on her right side in a close-up shot. In the next room-wide shot, she has suddenly returned to her back, and after he has left the next close-up shows her on her side again.
After Leonard drops his suitcase out the window, it isn't there when he goes downstairs to meet up with Michelle.
Early on, it is established that Michelle has a dog, Rex. Then the dog disappears. No one ever walks the dog. When Michelle is in the hospital or later laid-up at home, no one attends to the dog. When Michelle makes plans to move to San Francisco, no one mentions the dog.
Although there is a mention of bipolar disorder, Leonard's presentation seems to align with borderline personality disorder more.