When dealing with a teenage stepdaughter, tread lightly. Fifteen-year-old girls are experiencing a variety of physical and emotional changes, some that they may not be aware of or have difficulty understanding. They are making a transition between childhood and adulthood and are often overwhelmed by the challenges they face. Though she may be tough to handle, try to understand what could be going on in your stepdaughter's life. Before you react, put yourself in her shoes for a moment.
Take an active interest in her life. Ask her about school, friends and her thoughts. Listen when she talks. You may find at first that all you get is snide remarks, but stick with it. Attention may be all she needs.
Understand that she's going through changes. Though she is stressing you out, it's likely that your fifteen year old stepdaughter is stressed as well -- she may be encountering peer pressure or a lack of self-esteem. When she acts out, be firm but remain understanding. Don't let her off of the hook, but try to rationalise before you take action or speak out of anger.
Act first as a mentor and not a parent. If you are a new stepfather, it's possible that your stepdaughter resents you or the fact that her parents are no longer together. Try to be a supportive, positive influence in her life without trying to pressure her to play the daughter role. Step into the father role when or if it naturally occurs.
Participate or attend events that your stepdaughter is interested in, such as sports. Help to organise her birthday celebration. Offer to care for her when she is sick. Take her shopping for school clothes or give her driving lessons. These gestures will show that you care about making a connection with her.
Set boundaries and stick to them. When she misbehaves, such as breaking curfew or talking back, take away privileges. Restrict her from using the phone or hanging out with her friends. Alternatively, consider asking her what she thinks the consequences should be when she acts out. Do this at a time when neither of you is upset. Show her that you will follow through by taking action immediately every time she is disrespectful, and remain consistent.
Attend family counselling if you are unable to connect with your 15-year-old stepdaughter. The entire family may benefit from talking to a professional. There could be other underlying issues with your stepdaughter that you aren't aware of. A professional may be able to get to the root of the problem and enhance communication between you and your stepdaughter.