Its not just single parents this instance happens, one of my x friends were a married couple & they took the preverbial out of me - always on the cadge off me [yet had more income than me!!!] even food & stuff, money paid back if i was lucky late or not bothered, tho emotional blackmail with their kiddies alway got the better of me, till i realised i was doing them no favours anyway, because i'd always bailed them out. Soon realised this game & put an end to it by saying NO, so they had to do without whatever & look to themselves to sort their own budgets out - but alas was the type of people to find someone else to leech off but least it wasn't me from then on!!
Do not be a mug for this type of person!!! The longer u do this the more she will take especially using the kid to do it before u know it ou'll find it hard to say owt or stop - till that last straw creeps up. If she asks again in any way like this then say no, if your concern is the child then it is really upto SS to deal with that im afraid.
I have good friends that i help out no problems & they help me too [2 way street], as it should be
Harsh as it sounds but from experience!!