I think it depends on where she carries her weight to begin with. If she's big on top mostly, they'll go down, but it probably won't be a great decrease. Unfortunately, though, we can't really control where we lose the weight when we lose it. If we could, a lot of plastic surgeons would be out of business.

I, myself, carry my weight in my stomach, so when I lose weight, that's the
last thing to go, and unfortunately, my breasts and butt are the first to go. Conversely, when I gain weight, the first place it goes is to my stomach.