Will you get to see her in class before she goes to the Hospital? If not, you can go your principal for the following suggestions:
1. Take up/start a donation on her behalf intended for a get well card, ballons, flowers, etc.
2. Promote a Breast Cancer Awarness (with her permission) in her Name
3. Report the student and what he said to the Principal... and suggest that he and others might benefit from Breast Cancer Awarness info...
4. I would have clocked him anyway... but I can't recommend that one...
5. If any of that is beyond the scope of what you feel comfortable doing, you can always write her something, or simply provide a card that can be delivered via the school.
Bob D.