I did eventually notice there is a huge difference in her smile alone.
That is a sign of plastic surgery.
For me, the biggest change is her chin. It completely reshapes her face. The cheekbones take away the moon-face thing, too.
Her mouth does look a lot better - it doesn't protrude as much compared to the rest of her face. That may be because her chin and cheeks stick out further, though.
She also had some work done on her eyes - they are less hooded and fleshy than they were before.
I think that she looks very good. Not fake at all, and she still looks like Chelsea. Just better.