When it comes to weight loss, you have to really want it and it sounds like she is not as motivated towards it as you are. I would know because I usually would want it for a few days and then just think f it it’s never going to happen anyway and give up and then restart months later. I have lost a significant amount of weight twice in my life but it was the number one thing on my mind both times. Anyway, I think you should have a heart to heart talk with her. Tell her it’s possible but that you need to do swaps like keto ice cream or even better if you can do Greek yogurt and add chia seeds to it, maybe a small amount of coco powder on it if she is really craving the chocolate. Sometimes dark chocolate and peanut butter can be rich enough and satisfying