Weird sleepover situation. What does this mean?

You could be bi-curious or bisexual, and Friend A is surely either a closeted bisexual or closeted gay (the closeted ones have a tendency to talk too much about women and heterosexuality). This is only the first step in what will be a long journey of self-discovery, and don't see this as a bad thing. If you do like Friend A more than a friend, pursue your feelings. It could be very beneficial in doing so.