cats

Slow and steady on the weight loss: try using a little scale to weigh the usual portions you give her (you can include the scoop as long as you always use the same one) and after you have an average over a day or two, start making her new portion size just a few grams less. Between that and more playtime she'll slim down without being too mad at you.

If you have only been doing dry food you could also try changing one of her meals to wet food, keeping the same amount by weight. Dry food is more caloric per gram because water is heavy. The extra hydration will help her feel satisfied and be good for her kidneys.