What color corsage should I ger her?

Hmm. Hot pink? (poor girl) well, I would say white roses with a pink center and green leaves around it. Its pretty easy to find the roses.

Try small pink rose buds with white baby's breath. :)

White and pink would be a safe bet. This might be taking it too far but do you know if she's accessorizing with another colour?

Hot pink and orange are the in colors for the moment and a corsage doesn't have to be made of only roses. Maybe white roses and hot pink flowers as an accent?

Or you could try one of these....
http://www.flowerbarn1.com/prom.htm
u could try the...
Alstroemeria Corsage

Or, perhaps...
http://www.woodyaflowers.com/category_s/4.htm