Diving into motherhood with a teenager!

This is my first attempt at blogging. I am 40 years old and have never had any children. But my fiancee has a 14 year old daughter. I am jumping into motherhood with a teenager! How frustrating! For her and me both!
I have tried to be very open & honest with her and keep the communication line open. It is still difficult though. I get so frustrated that I have to keep asking her to do the same things over and over again. But when I was her age, I was the same way. I have to keep going back and remembering what I was like as a teenager.