it is okay for the crew to do their job. it is not okay to treat a client like they committed some type of crime (in this situation, at least). as the PO said, no signs were posted. perhaps the daughter should have been more careful, but i don't believe two wrongs make a right here. the way this employee handled the situation was definitely a wrong. but one which was intentional where as the PO's daughter's choice of clothing appears to sound like it was not intentional to offend anyone.
number one rule in good customer service is the diffuse a bad situation from getting worse. they could have simply asked her kindly to put on a cover/top and then return. it needn't have been that rude.