That's a heart-stopping post. Very glad to hear a positive outcome.
I think your babysitter is a gem.
If I may suggest:
1. A big tip (i.e., BIG)
2. A thank you note in the paper for all who stepped in to help
3. A letter of reference for the young lady, describing the event and how her attentiveness and prompt actions made a difference.
This should be the sort of thing she can include (photocopy) with her resume. In a tough job market, this could help make a high quality candidate stand out. She seems like the kind of person I would want as a nurse.