Tell my mother-in law off or file for divorce?

My husband's mother always has her hand out.  She has two sons and my husband is the youngest. She no longer asks her older son for money because he says no flat out without falling for her sad stories. Her lack of planning and lack of financial literacy always somehow becomes OUR problem. My husband and I no longer have a joint account because I do not want to help her any longer. We have separated our finances, but we still have a common goal we are saving towards. He can never get ahead because of her, and even knowing that he has a goal, she always has an emergency. One time he told her no and offered her help, by budgeting her money for her so that she was not overspending and taking care of her necessities first and helping her save and her wants last if anything was leftover, and she told him, as long as he had a job she would always have income, and he still gave in and gave her the money. It's ridiculous and I'm beyond over it. I'm at the point where enough is enough. He would tell her he would think about it, and then she would call him and say that she needed to talk to him in person, which is where she would talk thousands of dollars out of him.  She has always used him as an ATM, and I'm tired of it.  How are we supposed to get our savings where they need to be for our goals? Each time we get so far, her hand is out, and he goes into our savings to help her (Well, now just his savings, because remember I separated our savings). So, instead of building up the savings when he adds money, it is just replenishing from what he gave his mom. It's clear and obvious that the reason she didn't want us to get married is because she thought her money train would end and it should have. 

What’s your opinion 🤨?