Assuming the medication is amprolium, it won't affect her. It stays in a chicken's digestive tract and acts on the cocci they eat when they eat from the soil. It doesn't even affect the eggs. However, normally a broody's chicks pick up some immunity to cocci from the mama (from eating some of her poop.)
So, if you prefer to feed medicated, that's fine. If you don't, that's fine, too. What you DO need to be sure of is that the chicks don't eat layer feed -- which they will if they can, and mama will feed it to them, too. The extra calcium is quite harmful to their organs. The mama, on the other hand, can eat starter, grower or flock raiser. She won't even need the extra calcium in layer for a while, because she won't lay while raising her chicks.
My flock varies in age from a couple of weeks or so up to 4 years. I feed them all grower or flock raiser. I offer oyster shell and grit separately. The chicks will dig out small pieces of grit but they leave the oyster shell alone. Works fine.
http://poultry.purinamills.com/ASKTHEEXPERTS/FAQs/ECMD007942.aspx
http://www.themodernhomestead.us/article/Broody-Hens-1.html