D.C.
I'm sure this is not the easiest solution, but I would start looking for someone new. She doesn't sound like someone I would want with my kids. She sounds like she is not interested in the job anymore, for whatever reason. You don't want to trust your kids to someone who is not giving their full attention to them. Don't wait until they get hurt because she's not paying attention.
One more thing.....if she keeps making you late for work, you may not need a nanny at all...you'll be home all day when you get fired for always being late.