This all depends on the age of consent where you live. In UK, the age of consent is 16 therefore Buffy was well within her rights to sleep with Angel and he's done nothing legally wrong. Don't know what the age of consent is in California though.
Me, personally, the reason for age of consent (with adults) laws is to prevent child exploitation, including sexual exploitation. There are so many kids who are sure they're world wise who fall for the simplest of manipulation techniques (combined with the risk they tend to overlook, and the focus on the immediate moment) that it's sad. (And much worse, there are parents who will allow other adults to have sex with the kids in exchange for money, drugs, even just companionship, which happens too much already despite kids being unable to consent even if they wanted to.) If kids are mature enough to make decisions like that, and even more so for marriage (I know plenty of places allow kids to marry with or without parental consent based on age, typically younger for girls than boys), then they should be mature enough to make many other decisions that are sometimes barred to them, and they should be considered adults. For that matter, if a kid proves maturity and ability to support him or herself at age 15 (that is, becomes legally emancipated), then that should include the right to consent to sex with adults in my book.
(I also think it's ridiculous that here in California you can't buy cigarettes until 21, when you can marry, vote, sign contracts, and join the military years before that. I say that as a nonsmoker who thinks smoking is stupid, btw, it's just that law is more about imposing one's own moral values about a vice onto others rather than protecting vulnerable members of society, and I take a dim view of imposing one's morality regarding vices through the force of law, and that includes regarding sexual behavior.)
But that's beside the point. I was directing my statement to those who say Angel was robbing the cradle. If people are going to say Buffy is too immature to be in a serious relationship with Angel, then they should also be questioning the far more dangerous things she's doing. Giles may direct her actions, but he's rarely out there with her, meaning she's operating with a kid's poor judgment, and is essentially being exploited (actually, I think the show makes it clear that Slayers are exploited, but most people don't dwell on that too much).
But that's not how society sees it. It's like a movie in which a 13-year-old is living by herself (pretending her dad is still alive), drinks wine, doesn't go to school (though she's educating herself), cusses, and most of all kills, and yet most people are upset that she's shown being in a sexual affair with a 17-year-old...the older boy being disabled (barely able to walk) and a lot less world wise and scary than the girl is. On top of that they show the girl being menaced by a vile child molester who not only torments the girl and her boyfriend (and also uses racist terms), but takes the girl's beloved pet mouse and burns the eye out (this was shown in graphic detail that I so hope was fake, but being the 1970s I'm not sure it was) before tossing the mouse into the fire as an act of cruel intimidation against the girl. But still, people bitch about the consensual sexual relationship between her and the older boy than any of that, which to me is crazy (and typical)...and could be how people are affected watching Buffy with Angel.
