I am only speaking from experience my daughter, found herself pregnant at 14 and although it brought us closer together emotionally, it was not a pleasant experience.
She is now 18, more mature and a fabulous person, looking back she says I was just a kid - what did I know that something like that would happen to me. I have a 16 year old daughter, though she is pretty easy, but I was a troubled 16 year old once (and I have also transracially adopted a child with challenges).
Its a complicated situation ( late, international, cross racial adoption, early trauma,etc. I would very much appreciate just seasoned experience and practical advice .
Quite agree no preaching - if you believe your kid to be sexually active - and if it agrees with religious beliefs - I advise putting her on the pill.
You are obviously aware that a teen who is acting out like this will rebel against very restrictive rules, but that still leaves you room to maneuver.