I'd vote don't engage w/ MIL about it. Just tell her that it's W's life to live and that you're not giving up on her, but you aren't going to try and coerce anything out of her.
Keep up the GAL, expect nothing.
Me: 34 W:33 T: 10 M: 6 S: 6 D: 5 BD: 5/14 Still together(ish) Not giving up: 7/14 D talk has slowed, a lot. Gradually working on things together. Still separate bedrooms. Slow and Steady wins the race.