+1 Put the images in a password protected gallery
If she does not like this I would:
1st off, you had mentioned parents, not just her. This brings up a few issues, IMO. who are you shooting for? Do all parents care? or just this one out of 5 or 6?
If they all feel the same, then you should crop waist up. That is what they are paying you for.
If she does not want these online, ask for an email stating in writing the exact photos of her daughter that she wants taken off the public internet. Make her list photo number and player number. Make her do all the work.
I always shoot what the parents want. If they do not say so prior to the season, then my way is the best way. If they state, i.e. swimming or wrestling photos - no "bulges" below the waist; I make sure they are not in any photo.
Finally, I have had one friend shoot for a mom like the one you described. After hearing her numerous complaints, (i.e. her daughter's bad side; her rival on the team is in some photos; her field hockey uniforms shows under her skirt!!) He wrote VOID on the check, mailed it back to her with a nice letter saying the contract could be met by either party involved. This disagreement was unresolvable. He took down the gallery.
With in a week, she brought him cash. She now pays him almost double to cover all games. Almost triple. He moved out of state and she she still makes sure he is her guy. He also throws out any photos that could be risque, but still shoots every player unbiasedly.
That is not always going to happen.