I would certainly support my girlfriend in anything she wants to do, but since she's only 20, I doubt whether this procedure is in order for her, at least for another 20 years or so. If a woman has had a lot of kids and having the surgery is something she wants to enhance her own self-esteem (and perhaps her love life), then why not? As long as her surgeon thinks the procedure is safe and she can afford it, then I say go for it.