A mother of my DD's friend keeps playing the same game every time she wants free childcare. Near every school holiday she will contact me to ask if my DD wants to come over and play / sleep over. Of course DD wants to go so off she goes. Usually within a couple of days or so she will ask if I can look after her DD because she has to go out. Usually for a social occasion rather than anything urgent.
The last time I found out that when my DD when for a sleep over she went out to work and left her son to look after my DD and her DD.
It's coming up to the school holidays and I know this will happen again but I would rather avoid it. I am thinking of what excuses I can say without making it obvious.