Her body has changed ALOT.
I'm not really convinced that she had a reduction though.
Personally, my breasts change size from week to week.

It's very annoying, but it happens naturally. my ex said it was like I'd get a free boob job every month!
I was also anorexic at one point in my life and nearly lost all my boobage and went down to an A cup.

I'm usually a 34 between a B and a C. Some brands fit, and other don't (as every woman knows) I've even bought a couple of 32C, aswell. And sometimes I'll be poppin out of my biggest 34C bra, if I'm especially bloated.
Maybe her boobs just change drastically with her body, like mine do. If I lose weight, its all in my boobs and ass.
But than again, she's hollywood