My teacher kissed me/I kissed her... I have a girlfriend!?

I, personally, would tell my girlfriend... but, I'd be careful in how I describe it... perhaps omitting certain details... try not to make it seem like such a big thing, just tell her that your teacher kissed you... 'accidentally' but you have a suspicion it was on purpose. That way, you get the satisfaction of telling your girlfriend, getting it off your chest along with any guilt or other negative emotions and no-one freaks out and does anything drastic! <3