ZUMBA! I love zumba, and it is so hip and fun... but if she isn't into dance... kickboxing is a blast! Yoga, Tai chi?
Have her look at the DVDs on Beachbody.com they have all sorts. P90X is a pretty popular one, and is challenging, but is supposed to be loads of fun.
I used to do "yoga booty ballet" DVDs- so fun. In high school I took karate classes and did kickboxing. Zumba is a blast. If you have a game system there are some awesome workout games out there like wii fit and xbox kinect your shape.
Also see if your local REC center has gym equipment. Maybe she could afford a membership and go there to workout with friends? I used to go on long walks all over town with my friends in high school, play hack-a-sack in the town square, snowboard, and hike up our ski hill in the summer.
-M.
-M.