How do I not get strep if I am babysitting a girl with strep throat?

Strep throat. Strep is contagious through contact with saliva. So if you don't share drinks or kisses, you should be ok.
It's possible. If you have no tonsills, you may not get strep, because it has affinity to tonsillar tissues primarily, although, strep pharyngitis has been seen as well. It may also depend on the status of your immune system, as it may fight it off effectively.