What I've tended to do with other fannish daughters is tell them that they are allowed to yell, to make a fuss, to shout, to run, to do whatever it takes, if someone makes them feel uncomfortable or scared and that they can come to me, or to any other woman they know for help and we will give that help.
It should never be about how a woman or a girl appears or seems. It is not our fault. The harasser is the sole one to blame.