Does your daughter understand the mechanisms behind keto?
One thing that I’ve observed offline (because people online seem to be well read and invested in the mechanics of the diet) is that one person hears about keto, researches it, acts on it and has great success.
They then tell someone else, who gets the basics of it - but, perhaps like the situation with your husband, requires someone more well read to keep saying, “Yeah, you can have that, or a little of that, but don’t touch that,” - because they don’t understand some of the finer details.
I think the rest of the posters are correct when they say that your daughter has to want to make the change, but I also wonder if some of your daughter’s resistance is if she doesn’t wholly understand how keto works.
Rather than seeing this as a great opportunity to eat some wonderful - and usually ‘restricted’ - meals, such as lamb or beef rump steaks cooked in butter, or a burger topped with quality cheese and bacon, it seems that she’s focused on what she will lose instead.
Keto, to me, is not about what I can’t have - it’s about what I can have, but given that we’re all so indoctrinated with the food pyramid and slogans such as ‘5 fruits and vegetables a day’ and the standard western diet, moving to keto is a real mindshift.
The first few weeks feel like you’re fighting with yourself - for example, when you swap a bowl of strawberries with a smidgen of cream for a bowl of cream with a smidgen of strawberries.
The biggest change I struggled with was that I’d always cooked meat or oily fish in about 6ml of oil - and by the time any vegetables made it to the pan, the oil was long gone; I was essentially dry frying or adding some water to steam in the wok.
Having ditched the accompanying carbs, I now cook in 30-40ml of oil instead. I have far fewer vegetables, but they’re incredibly delicious because of how they’re cooked.
Pre-keto, there’s no way I could’ve cooked the meat/vegetables in such a manner - so being able to recognise what I am able to have and do is really exciting.
I think your daughter knows she needs to do something, and it probably all just feels overwhelming. It’s difficult, when you’re fully hooked on sugar, to accept that this is pretty much the end of the line for that way of eating - that you won’t have a doughnut on the way to work, or a chocolate bar at break. At that point, it seems impossible - but a few weeks into keto, your body doesn’t need it and doesn’t crave it. It’s just getting there.
As the others have said, it’s painful to watch someone you love making choices that you don’t agree with, but you can’t force the change.
If your daughter does want to give it a go, then I would suggest that she watches some of the videos or reads some of the literature to make sure she understands how it works.
You could help her by sitting down together and making a list of all of the meals that genuinely excite her - flipping the focus to what she can have is more likely to succeed than her focusing on what she can’t have, or both of you trying to find ways to circumvent the diet to mimic the foods she used to eat.
Best of luck; it’s a horrible position for you both to be in.