KrisandNika

Same sex couple here as well. Both female.
We just go married and just filed my AOS for my permanent residency. My wife is the US citizen. We married here in California.
Quick advice, don't forget to include which state you guys are going to get married and if that state allows same sex marriage. We have compiled clippings of news and the law that states it is legal to marry in California. I have noticed some same sex couples weren't able to do that but got approved anyway. But you know what they say, better to be over prepared than under prepared.
My partner and i are willing to help incase you have questions.
Good luck!!!

Sure you can. It can still be a short an simple statement even with that info. Something like, "We first met online XX/XX/XX, kept in touch through email and then began a serious relationship in 2011. We visited together on XX/XX/XX when I flew to see her in [city, country]."
It also depends on what country the foreign fiance(e) is from and where they will interview later. For some consulates you may wish to write out a longer, more detailed statement about your relationship and how and where you met. Some use a relationship timeline. You can do a search about it.