What a shame, such a beautiful body when she is heavier.

Not initially. A woman's breasts swell and get larger during breastfeeding. After nursing completely ends, they deflate sometimes and aren't quite the same as they were prior to pregnancy and breastfeeding. I know someone with an A cup to begin with, who said she noticed she got smaller after her first child.

Breastfeeding causes boobs to shrink? Lolwut?
Must dash. I forgot to feed my wombat.

No, she lost a lot of weight. Repeatedly losing a lot of weight (like when she gets super thin) and gaining it back (during times when she's healthier) causes breasts to deflate. Plus, she's had three kids and breastfed them all. But it's mainly the weight loss.