say it smells cheesy in here then smell ur feet, ask ur friends to do so, hopefully she will realize it by herself
It's a good question. If you don't say it, he or she will continue to smell, because he/she didn't know. So tell that people in a secret place, comforting him. You'll be a true friend for this person, because you save her from the disgusting "aaaahhh" from other people.