Here's what I think. The pictures octolina posted aren't a very good comparison in my opinion. Except for in Rule, GREEN, and a little bit in Days, the difference isn't very big.
But I definitely think she did something to her nose. I mean, when I saw NEXT LEVEL, I just did not see Ayu's old nose there at all. To start with, that area between her eyes looks very thin now. Overall, her nose looks a lot thinner to me, which makes it look a lot longer on her face. Also, I think the tip of it is a lot smaller now. Here's a picture for comparison:
Sure, she's smiling in one picture and not in the other, but honestly... I don't think that matters because in these pictures her nose looks VERY different.