My girlfriend wants us to be friends with a couple of guys she has had sex with before we hooked up. I say no way!! Question: Is this normal

Actually, it's not that unusual. A lot of women seem to be able to maintain friendships with people they've slept with after they've stopped sleeping with them.

I don't know if they're simply more mature than the average man, or just crazier.

Your decision is totally rational, but oddly enough, she probably felt the same way about her suggestion. I'm not saying you should give in, just that she wasn't actually out of her mind when she suggested that.