Wasting time with diets

My overweight wife decides every few weeks to try a new diet because she is not losing at the rate (or at all) she wants too. Never mind the expense of starting each one of these diets, all while we have a gym membership, she is now trying acupuncture, and wanting to get an additional gym membership that has private trainers you can hire. Doesn't understand why I get upset when I'm hesitant to spend money to change our lifestyles when I know its going to change again in a few weeks