Does she not work? Sounds like a very lonely lady that doesn't get to talk to adults often!!

Some people also just don't get hints (like you running after a bus). Sounds like you'll have to tell her incredibly overtly, "You can't stay and talk anymore as it is preventing me from caring for the children."

Go so far as to say "I almost missed the bus yesterday because you were preventing us from following our routine."

Hope she starts doing a quick drop off for you! Nothing worse than clueless people that just don't get hints!!