As an FYI to anyone potentially receiving misinformation, keeping a foundered horse THIN is completely incorrect. There is zero health benefit in keeping a horse underweight for founder as opposed to a proper weight. And if she foundered on grass, it is completely beyond me why you would half starve her as a supposed "treatment" and yet have her ON grass. It doesn't matter that she's "healed", if she's foundered once on grass, you can be pretty darn sure it's going to happen again, regardless of how skinny you force her to be. Horses don't need to be fat to founder, it can happen to ANY size of horse if they don't handle the sugars in grass and grain well.
I have never in my life heard of a vet suggesting keep a horse "skinny" as an effective treatment plan. They shouldn't be obese or fat, and that's about it. You're only putting more strain on her body by keeping her so thin, and likely to trigger another attack, especially if she's on grass and chowing down to replace her lost calories.
And yes, I've dealt extensively with founder/laminitis and known plenty of people who have dealt with it extensively.
SHe did not founder on grass she foundered on a dumb barn owner feeding an 800-900 lb horse a giant coffee can of grain 2x a day.
This happened 4 years ago. We tried many different options to return her hooves back to a normal state including natural trims along with soaking and oiling... and supplements etc etc before we (a DVM !!!! And I) decided to remove weight from her. The removal of the weight worked... everything else we tried did not. She is 100% fine and has been for the past two years.