Would you upset if u walked in on your daughter having sex?

I'f sex is apart of humans nature why would this make u mad? is 15 "too young" to have sex?

My friend's sister daughter had an early release day at school and apparently long story short her mom walked in on her daughter having sex. She was absolute okay w it but told her daughter basically to schedule her intimate time with her boyfriend away from their home.

My sister went on and on about how the little girl will grow up too fast! And a whole shit load of other stuff.

Does having sex early or "too young" have any negative affects if even if properly educated on sex?

Is it bad patenting to give your children this amount of freedom?