She has no reason to grow up. In fact, she's making a killing by not growing up.
This won't hurt her career, and will probably will help it. Eventually her looks won't help her, and she'll just have to rely on being stupid as a shtick. She's got the qualifications for that.
What is the shocking part is that she is 26 years-old, that makes her a full grown woman! By the way she is acting I would think she is a 14 year old suffering from PMS!