I think the practice in the Armenian Church is to only wash the feet of 12 men. The men, afterall, represent the Apostles, who were male.
Before we got our present priest, our church breifly had another one who was viewed by some as a bit liberal and too "Americanized." Among other things, he washed the feet of some women on Holy Thursday. He had 12 persons on the bema (in our church that's what we call the raised place where the altar is.) I think three of them were women. He washed the feet of all of them and then, if I remember correctly, a woman from the congregation came up onto the bema and he washed her feet as well. I was sitting in the balcony next to an elderly woman and I remember her taking part of the veil she had on her head and covering her eyes with it. It was as if what was happening at the altar was such an abomination, she could not allow her eyes to see it.
I won't give the details, but there was a lot of controversy over this afterwards.
My current priest washes the feet of 12 boys from the Sunday School up on the bema. Then he moves down to the part of the church that is in front of the bema (but not on it.) He then invites parents to bring their children and he washes the feet of all of them, regardless of gender. This has become a much loved gesture and the church unfortunately becomes a bit of a zoo with hundreds of parents bringing their children forth to get their feet washed and annointed by the priest. I think people feel it is a blessing for their children. The good thing is that this has brought many people to church who otherwise wouldn't be there and it has encouraged many people to enroll their children in Sunday School who otherwise would not be going.