Yes i heard that too. Some say she's had extensive plastic surgery but i dont think that she has because looking at old photos of her teens she doesnt look much different.
Plus, if she did have plastic surgery she would have had her chest done too!
I personally think her boobs look slightly bigger recently. Maybe a good bra but surely, being most of the time tabloid fodder and obviously very aware of her appearance, it was only a matter of time.