Breasts may change SIZE during ovulation, but not shape. This is a case of a difference in body fat composition. In fact, in most women, breast size INCREASES with age (look at Salma Hayek, Susan Sarandon, Marissa Miller, I could go on) but when there's significant weight loss (or gain) breast shape and size change pretty radically. Anne Hathaway is older now, but she's clearly lost weight during the time between Brokeback and Love & Other Drugs. I wonder if she's gained any of it back for Dark Knight Rises.
One can only hope. Because chesty or not, that girl is fine.