If it’s due to eating too little, she should eat more. She doesn’t necessarily need tracking or eating anything like you but she needs to eat properly for sure. One way or another. It’s up to her, we actually can do very little if it’s about someone else’s diet (except if the other person is a small child or very dependent on the food we prepare for them)…
I doubt she lost 6 pounds of fat in a week unless she barely ate while being very active, maybe… But if she loses just 1-2 lbs and she can’t afford that, that is a problem, of course. She needs to eat more. It doesn’t even matter if she gets hungry, I am almost never hungry when eating my meal, it’s not a required thing, at least to me. But if her current food choices are just too satiating, it’s an option to change the food choices (I usually use this when I have problems with my energy intake longer term) - or maybe the frequency of meals if that is possible. If I add an extra meal, I can eat way more. I may be not hungry when I sit down to eat but I get hungry after some bites.
It’s usually easy to add some fat to every meal… Drinking calories may help too… If sweets help her, well, eat more sweets if that sounds a good idea to her… I would choose sweets over carbs for sure but I don’t know how important very low-carb is for her.
Food without much work? There are zillion options, I don’t know her taste and restrictions. I eat some cheese or smoked pork and boiled egg or something. I can make food in bigger amounts and eat it for a longer time… I eat sour cream as dessert… Even a luxurious coffee can boost calories… I keep various meats and cheese at home to have variety so I always can find something nice to grab without work.