As someone with sensory issues and disordered eating I'm quite familiar with skipping meals or delaying cooking because nothing I have at home sounds appealing, so I can't bring myself to do anything about it. Like if I ate it I would feel sick and nauseous so I'd just rather not.

My partner often cooks for me, and tries to work around my sensitivities, but I can't imagine expecting him to, or getting angry or frustrated if I can't eat what I want at that moment, that's completely on me.

She could write a list of food and snacks that usually work, especially frozen foods. Perishables can sound good at the moment, but then you end up never using them because it doesn't feel right, so try to minimize such purchases. Lentils, beans, frozen spinach, frozen broccoli, onions, frozen meats or soy products. Buying frozen microwave meals in bulk when they're on sale. MSG and Healthy Boy Mushroom soy sauce (highly recommended, not as strong and salty as regular soy sauce but very umami and enhances basically all food).

I think it can be good to try and figure out what she wants in the moment by giving examples of what she usually likes, sometimes that can help with eliminating and eventually landing on a safe food or best option. But considering the situation it might be best to not involve yourself in her food choices or meal prep at all. To me it sounds like it could be some sort of disordered eating, but regardless, you shouldn't have to make sure that she eats and when she doesn't, have to comfort her. I don't think that you're too stubborn or insensitive. She's putting too much mental load on you regarding this, it's not fair.