Ah, good question -- especially as the movie has one scene of intentional self-parody. Given the chance to play the older sister of the lead in a movie she's wanted to do for years, Davis swallows her pride at being asked to read for a part and agrees to an audition. The scene she plays with an actor calls for her to be surly and resentful, but she thinks if she plays it young and girly she'll convince the director to give her the lead. To that end, she does a dead perfect impersonation of herself as a young girl -- the big Bette Davis eyes, the flirtatious manner, the lilt in the voice. It's the best acting she does in the entire movie. All wrong for the role she's supposed to be auditioning for, of course, so she torpedoes herself. She realizes this later, so that's an excuse for more scenery-chewing.
But I don't think that makes the rest of her performance self-parody, although I admit the thought did cross my mind. I think she was just overcompensating for a weak script. For instance, whenever a crisis arises in her life (about every ten minutes), she flops down on somebody's bed and cries herself to sleep. Had to sell off all her possessions? Flop and cry. Got locked out? Flop and cry. Got arrested on a DUI? Flop and cry. No bed handy? Okay, a sofa will do...flop.
A really sappy movie.