Hope she does well, Ghost! My thoughts and prayers go out to her!
What kind of cancer is it? Is it metastatic? (Did it spread anywhere?) Depending on the type of cancer and if it spread, the prognosis will vary. I had thyroid cancer and it's very treatable, but it doesn't use the typical chemo treatment.
How old is she? Is she in school? She may miss some days and that may affect her.
The best thing is to make sure the chemo team talks to her about the possible side effects of the treatment and to get ways to help her cope with the side effects. Chemo will do some nasty stuff to you. Chemo can (depending on the person/dose/etc..) make you tired. lose your appetite, nausea and vomiting, weight loss, loss of hair, affect anyplace that has soft tissue mucosa that replicates fast (hair, mouth, inside nose, GI tract (basically your mouth to your butt), finger nails, etc...).
I feel being prepared and knowing the facts helps the person grasp some control on the situation. And of course having a good friend like you to keep her company definately is a plus!