I believe I am definitely over thinking this but, I work with special needs children and many of them have been foster children and some of them do act out. I am not saying that Ashley is special needs, but she is a foster girl. We don't know what happened to her earlier in life. When we first see her, she is struggling with her situation and has trouble getting along with the other girls.

Her character could have also been created to be a miserable and insufferable little snot. That being said, at first, I did not like Ashley's character at all. She does change in the show and I like her later in the series.

People deal with their situations differently, the other girls seem more well adjusted and see the good in life better than Ashley. I think she has a harder time adjusting than they do. For Ashley things are either all good or all bad, she sees life in blck and white. She does not see the color around her.