I thought most states followed the 3 year rule, in which even an 18 year old could not be charged with a sexual crime unless the other party were more than 3 years younger. I guess I'm mistaken on that.
It sounds as though the younger girls parents most likely felt that their daughter was "indoctrinated" into the lesbian lifestyle by the older girl, and therefore waited to get the strongest revenge.
I will say that I do not think a 17 y.o should be having sexual relations with a 12 y.o., regardless of sexual preference.
As to age of consent...Alaska is still 16, but there are stipulations to that. No teachers, authority figures and so on. Hawaii and Idaho are 14, which I personally find a bit concerning.