In the LW's defense, she may have been the target of the same attitude in reverse in the past. There's a whole culture out there that prides itself on having poor manners and/or refusing to dress "up", and it seems to get louder every day; and this pride not only demands acceptance of its own low standards, but often attacks those with higher standards. (For example, in law school, I caught Dante from my classmates for not wearing jeans, or for fixing my makeup after lunch, or even just for having a hairbrush in my bookbag! Reactions ranged from diagnoses of poor self-esteem to being labeled a "freak". Yes, I got called a "freak" by adults seeking a license in a profession known for its expectation of good grooming...)
The temptation is strong, if you're a fighter by nature, not only to dig into one's position, but also to become aggressive about it and even judgmental. The LW may have encountered a lot of scorn for her dressy ways, and has her current attitude as an excessive reaction. Not that this makes it right, but more understandable, perhaps?
(Note: I don't know her, so I'm only speculating.)