Y'know what, why shouldn't overweight or "Full Figured" people cosplay? It doesn't mean a thing. Come on, we're just as pretty as any sticky string bean cosplayer. *raises hand* I am and probably always will be a Full Figured girl, and I don't mind, I'm pleased with how I look. Besides, anime girls, video game girls are unnaturally small. All I can say is you won't catch me running around in some skimpy barely hold your breasts in costume. The Lulu one was bad enough.
I give your friend a hug and suppor her 110% to keep up her cosplay. Its for her enjoyment afterall, not others.