I have no idea on this at all so would appreciate some perspective. On the one hand I admire her principles, on the other it seems mean and slightly like blackmail.
My BIL gave up employment a few years ago to run his own business. In the main it does well, but is going through a lean time at the moment and he is starting to make noises about needing his mum (MIL) to help tide him over until the next set of invoices are paid.
He's been with his GF for 2 years. They usually live pretty well with meals out and things. Because of the lean times they have both been cutting back. She earns 6 figures and as a result is saving even more money than she usually does. BIL has indicated that she saves several thousand each month. She isn't flashy at all and the salary comes with the job as it were, rather than her wanting to earn loads to sustain her lifestyle.
Over a few glasses of wine at the weekend I asked why she wasn't helping her partner out and instead expecting MIL to step in. She said that he can have access to whatever money the want if they get married. But she wont support him until then, even as a loan. I asked if she would actually marry him and she said she'd marry him tomorrow if he asked, but he doesn't want to get married.
So this is where I am struggling - I don't think my MIL you have to support him rather than his partner. She enjoys a nice lifestyle with him normally, and it seems bloody minded to go without because he is going through a tough few months. Equally she shouldn't have to support someone if she doesn't want to.