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.
"People are made for happiness. Rightly then, you thirst for happiness. Christ has the answer to this desire of yours. But he asks you to trust him." -St. John Paul II