I have just recently dealt with this same problem with my 4 yr old son. And from what I gathered, it is completely normal and yeah yeah yeah. But, I would say, if you've told her time and time again that she cannot do that in public, and she obviously ignores you and does it anyways, I would end the playdate, swimming session, anything, and take her home for a time out. Explain to her that she is more than welcome to explore her private parts when she's ALONE, ie- bathtub, bedroom, ect. I know it sounds perverse, because it did to me, but it is completely normal for them to want to explore. But, as for exploring in public, it is just unacceptable. If you've told her before, and she does it anyways, she needs to be punished, and maybe even banned from that activity for awhile so she gets the idea. My son continually did that and we grounded him from EVERYTHING; friends, park, pool, cartoons, video games, relatives, EVERYTHING, because he continually showed his privates when he obviously KNEW (as we had told him over and over and over) he was not to do that in public, and we havn't had an incident since. Sorry for the marathon, hope it helps.