Get yourself a copy of How to Talk So Kids Will Listen, and Listen So Kids Will Talk, by Faber and Mazlish. It gives you straight-forward and extremely effective ways to help your daughter identify her own emotional issues. And it will give you wise and practical tools to help her find solutions for herself (with your loving support, of course).
She may have the freedom now, for the first time, to get a bigger share of the spotlight now that her brother is on medication (I'm assuming this has changed his behavior). She may be confused, both pleased and horrified, and perhaps even a bit resentful – because she's getting more attention, because her own "flaws" and mistakes will be more evident without her brother distracting everybody, and because she's getting more attention for the first time and it isn't all she hoped it would be.
You will love this book. So will your daughter. And so will your son.