First off, I'd like to say that I hardly consider myself a "slayer" by any stretch of the imagination whatsoever, but I DO prefer casual relationships over going out on dates, meeting parents, etc. Yet for whatever reason society makes me out to be a bad guy because I don't want a traditional girlfriend; likewise they make girls out to be sluts, whores, easy.. you get the idea.
Go home and tell your mom you found a girl, but she's strictly your fwb. See how well THAT goes over.