Six months is about right, although I find it's often easier to separate earlier both physically and because I like to get the pigs settled into family/friendship groups as soon as possible. But I've never heard of pigs becoming sexually mature at three months.
And we name all our Saddlebacks except the ones we sell as weaners. Names just pop into my head anyway and I believe it makes the whole experience of pig-keeping more enjoyable. Yes, it hurts every time I take pigs to slaughter, but it would hurt anyway.
Good luck with Colin and the girls.