I have a vaguely similar situation in that my wife's mother is on disability benefit and needs cash from time to time. No problem with that if it wasn't for the fact that she burned through a reasonable inheritance in a couple of years and was forever buying brand new furniture, brand new car replaced after 1 year with another brand new car, new carpets, new TV, new laptop, cruise holiday, cosmetic surgery, rare breed of dog, new-you-name-it-she-got-it. Meanwhile there's lots of luxuries I want but don't buy because I'm saving money for the future.
Then once the money was gone she decided she wanted to move to a new council house somewhere else, I lent her some money to help with this (removal costs, some furnishings etc). A year later she is desperate to move back to the town she was in before, wants financial help again (by this point the repayments had dropped from £100/month to £25/month). I'd made it clear the first time it would be the last time, she had to be sure she wanted to move there. Anyway to cut a long story short, I then become the bad guy because I don't want to throw my money away bearing in mind she'd blown several tens of thousands of pounds in the space of a few years. Wife ended up helping her out a bit anyway by taking out a loan which then meant she started struggling financially so I've had to bail out anyway....
In summation I can sympathise with the OP, there comes a point when asking for help from family moves into taking the **** territory.