Most women have their boobs shrink if they lose weight- I know I do. Don't know how much by though. I lost 2 cup sizes at one point after losing about 7kgs.
They'd shrink a little bit, but not a whole lot. Maybe half a cup size or so. I used to weigh 180 and was a 38G, but then I lost 30 pounds and am now a 36DD. So they're still big, but I had to lose 30 pounds for them to shrink just a cup size or two, so losing 10 pounds probably wouldn't do too much.