I class them and classed my DDs as young adults, still needing guidance, but free to start to become their own person and in some cases that will include having completely different sex lives than their parents did, especially young women.
In the second instance, there are very few 17 year old young men that could sustain a relationship, unless bought up in a certain culture. Quite honestly, do you think that she's actually fell in love with him, to the extent that she couldn't see sense?
I was running my own home at 17, but in hindsight, I shouldn't have been, I should have been able to study and enjoy that time.
I think the same of the Mums I have met, living in Mum and Baby Units etc.
My DD met her BF at 17, he was 23, she was very mature and they started off dating, she wouldn't have considered it, if he'd had a child. At 19, she got pregnant, unlike a pp, I wasn't unhappy about that. Me and my eldest DD still see her as needing guidance, which she asks for, but we wouldn't try to tell her what to do.
Previous generations may have looked as though they had independence, because they worked etc, but the family and the Church, interfered, very often until the couple were 30+.