A girl that you are clearly macking on, but for whatever reason, doesn't see it or is able to respond to it. Her oblivious nature doesn't always reflect her intelligence, but can usually be attributed to lack of previous relationships/suitors or just bad social skills.
Mark: Yo I just bought Kimmy a $75 dollar meal at that fondue place with the dim lighting. She was like "You're such a good friend, Marky!"
Sam: What an oblivibiddie.