Anna - I can relate. My husband and I married four years ago -- I was "of an age" and had lived alone for over 20 years. An adjustment. Then his 19 year old son gets into a bit of a sticky wicket and we insist he live with us. As you say -- instant mother. There is a BIG difference between weekend visits and living there.

People have given you great advice -- set limits, establish rules and responsibilities, give her space yet not TOO much spare time.

Here's some of the things I learned...you will be watched ("I saw you leave your dishes on the counter.") You will need to be very conscious -- especially at first -- that you are modeling the behavior you expect. Sometimes there will be lashing out at you -- "I hate this place, I hate you" understand it has nothing to do with you in reality. It's about change, growing up, etc. AND... make sure YOU have space. It was very hard for me to adjust too. I only had to worry about me for so long it was difficult to feel such responsibility for someone else's happiness. (I said "feel." I know no one is responsible for anyone else's happiness but a teenager can cause you to question that!)

My stepson moved out in January and will start school full time in September. I am very proud of him and feel living with us was a little bit of the reason he turned around.

My niece will be moving into his vacant spot in June (She is in her last year of college here....) Here we go again.....