I'm wondering whether women travelling as part of a family group aren't shown on the passenger lists? I'm having the same problem as you, I can find my great grandfather but not his future wife. I know the approximate date she must have arrived, but there doesn't appear to be any record for her or her sisters. Family folk law said they met on the boat coming to England, I'm not sure about that, although as they came from the same town they probably knew each other. They definitely married here though.