Co-writing has been a really interesting experience like nothing I've ever done before. I really hadn't realized until now how much I need to be in control of every element of the stories I write. I think co-writing something just takes a different kind of skill set than writing by yourself. I think a lot of writers can do both but I'm not sure I can.
There is a time when I write where it's just me, my computer and the characters. Later when it goes off to beta readers, or publishers and editors, and finally readers it stops being my story in a lot of ways. When I'm writing it though, writing the first draft and just getting it on paper that space is mine and mine alone and I really, really don't like sharing it. It makes me feel like a toddler stamping my foot and crying when I'm told I need to share my very favorite, special toy.
There are other things about it too that are hard. I don't feel like I need to physically watch her type scenes that I'm not really a part of and she wants me to be their chatting online with her the entire time. We also have very different rhythm to our writing where she writes slowly, deliberating over every word. I tend to write fast in short bursts, hammering out two thousands words or more almost as fast as I can think of them in one long narrative stream and then going off and doing something else for a while. I've gotten frustrated watching her slowly work through a single paragraph. She's gotten frustrated when I just go, and four pages later she's gotten no input into it at all.
So at the end of the day I feel like the story will be good but I will probably not be co-writing anything again for a while at least.