Where to begin? As a short intro, i met my wife almost 9 years ago and we started dating. After the first year we got engaged which went for 2 years and we then got married. I had never been a parent before. Her kids were 12, 11, and 8 when i was first introduced to them the 2 oldest were her boys, the youngest was my step daughter. 
 

over the years me and the boys got along great, even the step daughter and i seemed to get along well when she was young. But as the years have passed im witnessing a distance the step daughter has placed between us. Now im not one for needing us to be the best of friends but where things are now feels strained to say the least. To give an example. If its a simple interaction or ive gone to get something she asked for(usually means walking to the store as i dont drive) we are ok, but then she hides away in her room. I dont invade her space. Her room is hers. But if something happens like happened on a recent road trip i feel like the step daughter wont let me even talk it out.

We were going on a trip as my wifes middle child was graduating from Basic training. 11 hour ride in the car with my wife and my step daughter. At some point my wife stopped to refuel the car and though i started to get out to pump gas my wife stopped me as it was cold and i had removed my jacket to be more comfortable for the long stretch. While my wife pumped the gas me in the front passenger seat and her daughter directly behind me were minding our own business. At one point my wife said something which may not have meant anything important, but as my attention was not directly on my wife at that moment i was not sure. I asked my step daughter, "what did she say?" And the response i get back is an annoyed " I dont know!" Which by itself as she is a teenager i am not bothered by. But, my issue and why im writing this to begin with is, I responded calmly, saying simply,  "there is no reason to yell". Before i even finished the thought, she yelled back at me, that she knows she shouldnt yell but she is. At which point i dropped the whole thing and buried myself in the book i had brought. My wife either didnt hear any of this or chose to ignore it or something because she didnt mention it when getting back in the car. We then drove on. Though i had dropped it, it began to bother me that telling her she didnt need to yell would cause her to react as she did . I mean its not as if i was wanting to tell her to do anything more than acknowledge that i was aware that it was not that important a question. But the event had happened. Now, after some time had passed we stopped at a taco bell for dinner and my wife had to use the bathroom. Again me and the stepdaughter are alone together as we wait for my wife. I turned to her and i will admit i let my emotions get the better of me a bit saying, "listen to me!" But before i could get anything more out, intending to tell her that yelling like she did hurt my feelings. She yelled again saying that we were in a taco bell and this was not the best time. Of course it was late and the lobby was empty and no workers were in view when i chose to speak. In truth, with past experience if this had happened when we were home she would have yelled at me and gone to hide in her room. As it is she ended up going to stand outside until her mom returned. At first my wife witnessing our dust up, seemed to side with me turning to her daughter surprised at her reaction, but almost a moment later turned to me and just told me i should drop the whole thing. I did but the rest of the trip i was bothered by that event
 

now, i know i am not perfect and i have yelled in the past, at times i shouldnt. But now i cant stop wondering if i am in the wrong and whether i am doomed to have a stepdaughter that hates me the rest of my life. I feel hurt and confused and unsure what i can do to even begin to repair the relationship with my step daughter, the yelling does neither of us any good. I just feel lost, any thoughts would be appreciated.