Welcome to Gaia! ::

Alright then. I don't know what to call this, probably because I haven't done research on it yet (I tend to come here first when my superior intellect can't solve something.)
But here it is:
Me and my friend are completely opposite in personality, like I'm one of those naturally apathetic people, she's blindingly loving and happy, but we are the same on everything else (music, books, hairstyle, politics, theorem.) But lately for some odd reason, most likely the CIA pumping gas into my house, but I've been getting unreasonably happy, like just nervous energy making me giggle and seeing the world in rainbow pastels.
But the happier I get, it seems she gets more and more cynical and sad, without knowing why. She is even considering quitting with relationships ad the such, something I had done previously (I'm happily taken now, by a sadistic crazy, of course.)
Any thoughts, as in could this be my fault, or we are connected in some way?
Just saying, because I experienced that apathy and such, and it's horrible, and if it is my fault she is like this, then, well, you get what I'm saying.

If I had to guess, I'd say that this would be more of a psychological thing. While I can't speculate on the cause of your random giggling fits, the rest is fairly simple. Since you and your friend have become accustomed to a relationship in which one of you is cynical and the other is happy, your change triggered a change in her to compensate. In this case it's simply a subconscious reaction to an emotional stimulus.