not to be an armchair psychiatrist but you might want to suggest couples' counseling so that you can get her into counseling. What she's doing sounds familiar to me.... That's all I can say. Really you have to be willing to go into counseling because up and saying she should go is not gonna work, trust me on that one.
I wouldn't chalk it up to a "this is how women are" thing, at least from the way you described it in those short details. If you intend to be with her in the long run, then consider couples' counseling and talk to her about going into it. Erratic mood swings are not normal; even of women.
She sounds like she is a narcissist, the real type not some word just to use. I know because I grew up seeing EVERYTHING he described, and then dated women like that. Most people are narcissist, but when you deal with an extreme case, he is going to feel like he is going crazy, trust me.
She won't go to the counseling because she doesn't think anything is wrong with her, she just wants her way. If you don't go along with it, she WILL make you pay for it somehow.
Also, if she wants kids, he better watch out because she WILL do something to make sure she gets it. She will either trick him to get his sperm OR she will get pregnant by someone else, and say he's the father.
I recommend he leave her before he falls deeply in love with her, and it will be hard to leave. He just needs to make HIMSELF look bad, and use that as an excuse to leave because he makes it out to be her, she will make his life harder. She may spread gossip about him or claim he did something foul, I don't know, but it won't be pretty. He can be nice to her, but he needs to keep space between them for HIS safety.