[superasn]

Speaking from my own personal experience, the most important thing about your co-founder is that she must be good at things you're not. If both of you are good at the same things then you're probably doing it wrong.

Also like that e-myth book, make sure whatever roles you're going to be taking, it is in writing and there is no confusion about who is doing what. This is especially important when the day comes and you have to take a big decision about your company and she sees differently than you.