i don't think those photos are 100% photoshop..
i believe that it is the types of clothes she wears and the type of bra she wear.
If you notice carefully, in some of the pictures, she stretches her body.
and the first picture that koshka posted, that black dress, with the leather-liked thingy on the chest part (well, i don't know what it is called), its actually very tight and it squeezes her chest, which is why it looks as if ayu has big boobs.
hmm.. i'm not really good in explaining it.. perhaps it's time for a thread in explaining the types of bras and body parts or something
hahaha XD