this sounds familiar, though i will say I actually like! the thought of a woman worrying about seeming predatory, since it has always felt to me that as a man I'm under really strict cultural sensor on this, and there have been a couple of occasions when something which has been overtly s/xual and would be considdered extreme harrassment if the genders were reversed has made me feel awfull, especially considdering my abuse was essentially gang rape by and s/xual humiliation mostly by girls (though boys were present).
I'm not however concerned about the romantic end of physical affection here, indeed I can't really apply! any of those concepts to myself at all, I just want to get a little more used to this. I am fairly certain the kiss on the head was! indeed just friendly affection, however it is A, how I should respond and B, what from me would be considdered a correct! response that is my concern, since if (even as a friend), I hugged the female lead in a similar way at a similar time I'd feel as if I was being ridiculously too invasive and pushy.
Heck, while I considder that particular girl a friend I am not! in any sense attracted to her, indeed I'd feel the same concern about affection with any of the guys, and in fact while it is rarer this is one circumstances where guys do! occasionally hug each other or give pats on the back if they are feeling close enough, though it is still less common than with girls.