Yup, read all the threads, she's a cheeky fucker alright, actually slightly unhinged I think. Lost any grain of sympathy I might have had with her when the 2 weeks in Disney came out.
The problem is, people think you will just do it as it's the kids that suffer if you refuse. I have a 'friend' who does the same with her dog, I know if I say I can't look after the dog she'll just be left on her own, so I end up doing it for the sake of the poor dog.
Ex (who I still have to live with for now) works at home a lot and is always being asked to just have someone's kid after school, feed their cat, walks their dogs, have their dog/s overnight, sit in their house for a parcel, go over for the boiler man, collect their kids from school at the end and sometimes in the middle of the day if they are sick, have their kids here as they are too sick to go to school today, take their car to the garage (oh, and can they borrow his?), take their kids to after school club...etc etc. Often with the associated 'it's OK for you, you're at home anyway'. But he does actually have to WORK :)