I've dealt with similar issues. I don't yell, I tell them what's going to happen. In your case, I'd tell her that if she wears legs with any shirt again, they'll be gone for 6 months. Then if they try again to get away with it, I settle the issue and while they are away at school I remove them from their drawer and hide them somewhere. In 6 moths they will have found a new favorite way to dress. Then I bring them out and see if they can handle it better. I put it on my calendar to reintroduce it.
" I object to violence because when it appears to do good, the good is only temporary; the evil it does is permanent." Mahatma Gandhi
"This is the ultimate weakness of violence: It multiplies evil and violence in the universe. It doesn't solve any problems." Martin Luther King, Jr.