I have no problems with people having cosmetic surgery. I do wonder why her parents never paid for it before this after all they could afford it.
This is not the first plastic surgery that Chelsea has had, this is at least the second. The first one gave her a little chin and a somewhat smaller nose. I think that they are doing it a little bit at a time so that it won't be as noticeable, just like they did Hillary. If you look at that old picture of Hillary and Bill and then one from the governor's office and then the Whitehouse, you will see that Hillary has had many surgeries.
I think reputable plastic surgeons recommend waiting until the bones are fully grown (usually around age 20 or even a bit older); obviously, they'll start on someone very young with severe deformities, but that usually involves ongoing correction into young adulthood.