This article from the New York Times Magazine discusses how women are socialized to allow touching that makes them uncomfortable -- mostly in social situations, but also in intimate settings.
I recognize the seemingly minor things although I haven't experienced the type of sexual incident she describes as a pre-teen.
As the mother of three daughters, I am trying to think of ways to avoid this. I do not encourage them to hug or kiss people if they don't want to. I have also taught the oldest (preteen) to politely avoid unwanted hugs by extending her right hand for a handshake.
All this seems hopelessly inadequate -- what ideas do others have?