It depends. I got married at 21 years old. We didn't live together before marriage, and that marriage lasted less than 3 years.
I lived with my second husband almost two years before we got married, because I had no desire to get married again so soon. We have now been married over 16 years.
Really, we are not talking about a 16 year old in the back seat of a car. She is 29 years old.
Do you really think that she was going to stay a virgin until 29 years old, whether she lived with him or not?
You wrote:
“Do you really think that she was going to stay a virgin until 29 years old, whether she lived with him or not?”
Yes, if she believed it was important and moral. I have a 31 year old friend getting married in October. She’s a virgin. She’s also gorgeous and was always pursued by men. A 32 year old friend got married in December 2009. She was a virgin. She’s attractive and very athletic. She never lacked for male attention and was engaged once before. Both of them are devout Catholics. Both, not incidentally, studied and teach Theology of the Body. That’s not a coincidence.
So you think a parent should recommend to his daughter that she have sex outside of marriage?