As soon as females hit puberty this shit starts for most of them. I remember teenagers talking about marrying a guy after the first date and coming up with kid names too. And then they wouldn't go out again, so it was a couple of days of crying and then onto the next victim (guy). This one is the "one" and she is going to marry him and they'll have kids and let's speculate about what their kids will look like, even though they have yet to go on one freaking date. And heaven forbid they find a guy that wants to continue dating them or be their boyfriend, because then it is obsessing over every holiday about gifts and whether or not they'll receive an engagement ring or at least a promise ring.
I recall never having a time when all my friends had a boyfriend at the same time, so someone was always in the crying 'cuz he doesn't want to be my boyfriend stage.
And if they do become engaged they tend to be 100% obsessed with the wedding and it is all they talk about-the wedding or their future.
I had a very difficult time humoring this weird behavior, let alone participating. I felt like an alien. Teenage girls left and right were throwing away their academics and futures for this crap.
By the time females like this hit their twenties, they're a little less crazy than teenagers. But for most of them their lives revolve nearly 100% around relationships, dating, boyfriends, baybeez, marriage, etc.