re: How would you handle a financially irresponsible mother in law?

In the past I had a similar problem. I eventually, with her permission, gained access to her checking account online--not to use it but to monitor it. It was eye opening. Home Shopping Network was the big winner to the tune of the hundreds per month she was asking for to pay for needs. That stopped immediately and so did the request for money. If you do not have a firm handle on where her money goes, don't give her any. If you do have a handle and it is spent on unnecessary things, like 5 bottles of wine per week (she is an alcoholic, too, I am guessing), then don't give her any money. If she will not be financially transparent, do not give her money.