Well all of your advice is good.
On her breaks if you could get her to bring a natty PB sandwich on double protein bread in between lunch, maybe a can of tuna last break?
I would say tell her to let him make fun. All that is, is his insecurity that if she loses weight and other guys notice he just might lose her. Nobody wants to stay with an ass forever.
Get her some cheap weights at Target and teach her some things she can do at home after he goes to bed, or ignore him.
Like tricep chair dips, laterals holding something, push ups, chair squats. etc.. Milk jug deadlifts..lol Anything done at the gym I've found can be modified for home.
Walking the dog is good if the dog is not so ill behaved that she shortens the walk to get it over with.