Congrats on your D becoming a teen! Mine became a teen the day after 911 - the week her dad took off to join the circus. It was a difficult time.
When my D turned 20 I remember priding myself on the fact she was attending college, did not get pregnant, was not a smoker and had never been arrested - LOL!
Single parenting a teen daughter has it's difficulties and its drama but it's our most important role. Stick firm with your rules (everyone needs them) and love her throughout it all. Make sure she knows she can turn to you. No Matter What!