So a little background first. I do not have children of my own but I come from a large family. My husbands 15 year old daughter just moved in with us full time in June. She has a 16 year old boyfriend who she started seeing before she moved in. Anyway they've been together for 6 months now. She requested getting on the pill and as much as her dad didn't want to do it it's better to be safe than sorry so he took her to the doctor and got her on the pill. So anyway yesterday her boyfriend was over and my husband had to work and I also had my niece's birthday to go to so he told her that she and her boyfriend would have to babysit her younger brothers for a few hours. The rule in our house is that they are not permitted to go to her bedroom and were told to stay in the living room and keep an eye on the 10 and 7 year old brothers. Prior to me leaving I told them to stay on the couch and that either her dad or I would be popping in on them to checkup. Well I did pop in an hour after leaving and the backdoor was locked. I knew immediately what was up. When I came in I asked the 7 year old where they were as they were not in the living room and he said they went downstairs to cuddle. I was furious. I yelled downstairs for them to get upstairs right flippin now and they did not respond. I asked the 7 year old how long they had been down there and ge said it had only been a minute. I went downstairs and her bedroom door was shut. I banged on the door and yelled that they get the *bleep* upstairs right now to which she responded ok and they sat in the living room to which I proceeded to ask if they were really that stupid to do this while babysitting to which she replied "yeah". I called her dad and made him come home to deal with it as I try not to overstep my bounds as a stepmom. I then went back into the living to sit and wait. Neither of them would even raise their heads to look at me. This is the first time I ever yelled at her. The boyfriend got taken home and I went to my niece's party. Upon returning the teenager was in lockdown in her room. When dad went down to tell her dinner was ready she told him that she didn't want to face me. I told him that I felt badly for losing a grip and he had told her that I wasn't mad at her but that I was disappointed and that I wanted to apologize and she was shocked at that and said why would she apologize and he told her because I used an explicit word when I told them to get upstairs. I did and I felt horrible about that. She finally came up and the awkwardness was gone instantly as we do have a very good relationship. He does think that I over reacted a bit I yelling as I did but it all happened so quickly and I don't yet have the skills of a parent to react in any other way than I did. How could I have better handled that situation? I want her to respect me as a mother and to abide by the rules and not walk all over me because I am too nice at times and being a stepmom I don't have the same authority as dad. As I see it she is my daughter and she needs a good female role model to teach her what has been neglected to be taught. I told her yesterday morning prior to this boyfriend mishap that we would go shopping to look at homecoming dresses and I was going to cancel that but it may be the perfect opportunity to have a talk with her.