For BREAST cancer, that is the correct treatment... and better to do it immediately, to minimize risk that the cancer may spread. I think she's got guts to make the right medical decision despite changing her body image.
I hope she stays healthy and happy and doesn't fall into the booby trap of putting too much emphasis on breasts as THE sign of femininity. Sheesh- she's a cutie; somehow I doubt anyone will think her less of a chick!

Not to mention that now there's going to be a gaggle of plastic surgeons clamoring for the chance to be The One Who Gave Chrissy A New Rack.