I actually didn't mean teaching her about healthy eating. Really, if she wants to learn, she will. In general, parents don't like to be lectured by their children on
any topic.
I meant more saying things like, "Mom, thank you for paying for my weight loss membership. It's helping me a lot. But it's very hard to follow my plan when I have face junk food in all the cupboards. If the rest of the family has to eat that stuff, then can we put the junk food in a cupboard by itself where I won't be as tempted?" Or something like that.
Whatever you want her to do. Be calm. Be specific about what you would like her to do or not do or not say. Be grateful. And be firm. Takes practice.
If she gets defensive anyway, try agreeing with her first, "I know. I know you're trying to help me. I know you mean well. But this is not actually helping me. It's kind of making it harder. Please stop." See how gentle and respectful that can be without giving in?
I have no diet experience, but I have plenty of dealing with mom sending mixed messages experience.