I suspected as such. My grandpa does the same thing. Honestly, I would make her get up and get something if she wants it. (Within reason, obviously. I’m not suggesting you make her vaccuum the house by herself.) Also maybe instead of doing simple tasks for her, guide her through the task and let her be the one to actually complete the task. That’s what I do with my grandpa when he needs to use the microwave, make a phone call, put his dishes in the sink, stuff like that.
I used to cook when I was alone, but when I joined a group home, I felt hurried and careless and couldn’t cook with others around. I’m just wondering if this could be your mother in law’s problem. Maybe you could promise to stay in your room while she works if this is a possibility. It’s paranoia, I know.
I’m on team Just Say No. if she really wants something, she can do it. If she doesn’t do it, guess she didn’t want it. If she complains, tell her that it’s good for her recovery. Or just put on headphones and ignore her.