True, but one thing that occured to me is that it may not be 2.5 years since she actually lost the baby fat. I know some women lose it right away, but others take some time getting it off - esp. if they're breastfeeding (I know that's supposed to help, but it seems not always).
Anyway, I agree that if the skin hasn't tightened up mostly by the time the person has been at the lower weight for about a year, then it probably isn't going to.
If it really bugs her, the surgery is an option. The only suggestion I'd make as to that is to consider waiting until after the youngest child is old enough not to expect to be picked up. After my TT, I picked up one of my nephews and put him right back down.