M.H.
I wouldn't use her again. This has always been one of my concerns and I have drilled it in my girl's heads. They both babysit and one little peep out of a baby and they are running to the room to see what's going on. My youngest can sleep through a tornado alert but if a baby scoots down the bedsheet, she is up and running. I know that everyone is different but I also know that when someone has entrusted you with their child, it's a big deal. Babysitting is a lot more important and critical job than many take it to be. My girls know to call 911 in an emergency but they also know what to do if 911 doesn't get there quickly enough.
There are plenty of teenage girls that want to work. Find one that you feel comfortable with. She's out there somewhere.
M.