Of course it’s your business when you are going to be stepping in when she runs out of money, but there is nothing you can do to stop someone spending own money. You can make it unpleasant and if the person lets you put in controls that can be done, but bottom line that is the person’s money and that person wants to blow it sooner rather than later, can’t do anything legally about it.
My MIL would not pay her bills on time. Or at all if she could get away with it. It was her money, and though I could have paid her bill and then tried to get it reimbursed (fat chance!), I could not force her to pay for it. Not legally either Yes, I could forged her signature or attempted to bully the money out of her, or try to set up the auto pay, but if she set her foot down, and wanted to use the money to buy some more FRanklin Mint collections, that was her business, and bottom line there was nothing legal I, or anyone else could do about it.
She refused to sign somethings–DH rageds, she cried, went into cataplexy, but what can you do when it’s not your money and you don’t have the control and the person is still too competent to get guardian ship? Yes, it is her business, bottom line, because you can’t MAKE someone spend or not spend his/her own money the way wanted.
She knew her banker, and anything one put in place, like auto pays (still recommend trying to get them in place), she’d have removed. She wanted to pay the bills personally the absolute last day they were do. And she did suffer some dire consequences for the stupidities too. She sat with a broken hip at her house for a couple of weeks. That’s how stubborn she was.
But yes, bottom line, its HER choice. IF you can legally get around her somehow, that’s a whole other thing. But she has her rights. YOU don’t have to pay for when she goes broke. That is a choice of YOURS, But she has her rights and her choices and unless you have a legal basis, you can’t stop her from spending her own money even if that means she’ll run out and then you are on the stick for her You can get off that stick, but you can’t stop her from running out, not legally without certain things in place, and then it can even get to be an ethical issue.