I write to ask if it is wrong for sisters to share communion among themselves when there is no brother around.
The Pharisees came to Jesus, upset that his disciples were not following the traditional handwashing rituals prior to eating. But Jesus asked them, "Why do you yourselves transgress the commandment of God for the sake of your tradition?" (Matthew 15:3). There is nothing wrong with washing your hands before eating, but to elevate a tradition and make it into something equal to a command of God is wrong.
Look through the entire New Testament and you'll find nothing regarding who may serve the Lord's Supper. The reason we have men serve the Lord's Supper is that we typically have the servers make a few remarks about what we are doing and to offer prayers. Women are not allowed to teach or hold authority over men (I Timothy 2:11-12). But if there are no men present, then this is not a problem. Women are not allowed to address the assembly (I Corinthians 14:34-35). But again, the problem is that women are to be in authority over men. If the entire assembly is only women, then this is not a problem.