Hi Violette,
Welcome to the sleepless night's courtesy of a teenage daughter's club!
There is little you can do.
You have to trust her to make the right decisions and really, it's rarely serious at 16 and when the boy breaks her heart that is when your going to want to hunt him down and chop off his wotsits!
My daughter is almost 18 and I remember the first boyfriend she had at 16, he went off with her friend. You will not believe the tears and it's no good saying to her it was not serious, you'll see in time, to her, it was everything in the world.
Your going to get nightclubs soon. Alcohol, staying over at a friend's.... Nothing you can do about it except monitor her, I have (please nobody yell) read her diary, I do not see it as invasion of privacy, I see it as keeping tabs on her as things are different today than when I was her age and I just speed read it really, watched out for key words to see if she was okay not in any trouble. I know it's wrong, but, I was watching her back. She never knew, I would deny it outright!
As long as she has a good head on her you have little choice but to let her grow up and make her own mistakes, as heartbreaking as they will be for you her mother, you have to let her do it.
It's horrible. Really horrible. I would like to keep my kids in the house as soon as it gets dark and all that stuff, I do still with my other children as they are younger - but at 16, you have got to let them go to an extent as they will never learn life's lessons if you mother them too much.
It's horrible.
Good luck.