@Yellowirina Separately, we've been writing since forever. I wrote my first story when I was like eight. (To which I gave to my mother and she was like "That's nice, dear.")
I finished my first complete YA manuscript my freshman year of high school, which will certainly never see the light of day ever again. But I still remember when I decided to just go wild and simply start writing on my winter break, when it was California-cold and cloudy and I had the computer all to myself, and so I just wrote and wrote with no idea where it was going. Best feeling. I never stopped after that.
But together, we started with RPing together in AOL chatrooms. Mostly Sailor Moon RP which wow we haven't changed in fifteen years. In high school, we started doing the same, but with more original stuff, and then it slowly evolved into writing actual stories together via Livejournal. I used to sneak replies during class since she was three hours ahead of me.
But now like 99% of the stuff we write is collaboratively, over the much more useful Google Docs. Actually, you can read all about that in an interview we had with one of our favorite writing help blogs on Tumblr:
http://fixyourwritinghabits.com/post/125589806398/publish-your-stuff-interview-sarah-godfrey
We also write a LOT, all the time, every day we can. We've probably written a whole library by now, but we didn't keep track in the beginning, because when we finished books, we just moved right on to the next.
We kind of still do that. OOPS.
Thanks for your question!