Really, I wouldn't embarrass her. She feels comfortable in what she's wearing so it's obviously not bothering her If someone had pointed something like that out when I was at that age, I'd have been mortified and not gone swimming for a very long time in anyone else's company. In fact, I still feel very uncomfortable swimming without shorts on because a few years ago someone pointed out the tops of my thighs were hairy and I should start shaving there too... I still feel that way, even though I took their advice!