[markitcat]

Please, walk away from this situation. Whatever you do or say is going to be twisted so you come up looking like the troublemaker. She reeling you in, you gotta get off the hook.
This mil is controlling everyone with money. You didn't take that bait so now she's trying to control you and your husband with her money problems. Setting it up so your scrapping with the other siblings. This woman is manipulating the situation. Disengage, go back, run away. Danger, danger, warning, warning. She came to you asking for help, now she won't take any of your suggestions, and is backstabbing you by fanning the fires between you and youngest son. Your intention was to give her finacial advice which you've done, don't get sucked into this mamma drama. Now that I have your attention, You don't have to be rude or cruel in letting go, just step back and emotionally disengage from this situation. If she asks for advice, give it because it sounds like you have a grip finacially. Keep the emotion out of this situation. Your Mil is also an adult who should have learned how to say no to her children before they could crawl. So she taught the youngest son that she can't say no to him.