Room mates dog

Question
I moved in with my room mate about ten weeks ago. She owns a two year old female pit bull. At first the dog was very reserved with me. It took some time but after a week or so she was playing with me and not nervous when I was around. After going on a walk with her one day with my friend and seeing her pulling on the leash and not listening to her owner at all I decided that I would start training her. Now she completely listens to me. I take her for walks in my apartment community with only a leash in my hand not on her. To the point that she went to chase a cat the other day and all I did was call for her and she came right back where I had her sit and I put the leash on her. Problem is that when her owner is home this all goes out the door. She won't listen in the least bit and even growls at me when I get close to her owner's bed. If her owner is home first I am greeted with jumps, barking and even playful nips. None of this is true if I come home first. It's as if she is a totally different dog when her owner is home. What is going on?!?

Answer
Dogs are situational and she is probably is seeing time with you as one set of rules and time with your roommate as a different set of rules. Is your roommate interested in working on training her too? If so, that might be a great way for everyone involved to be part of keeping her mindset positive with everyone living in the home.

I'll include some links for you for additional training information. If you have additional questions let me know.

http://outlawchinooks.com/Pack_Leader.html
http://outlawchinooks.com/articles.html
http://outlawchinooks.com/index.htm
http://rileytrainingcenter.blogspot.com/