I don't want to loose her trust help?

Okay well to start things I have been with girlfriend for a little over a month. Her parents love me I'm there daughters only boyfriend they allow to stay at there house. I stayed four nights there last week. I sleep on the couch my girlfriend sleeps in her room. I respect they even allow me to stay there. Now well her mom(stepmom) lets us get away with alot more then what her dad does. Not ual in any way but just joking around. She said it's been bugging her her how my girlfriend does things in front of her that she doesn't in front of her dad. What should I do her act like I do in front of her dad in front of her or what? There kind of strict we discussed no until marriage. I got to know most of her family and her step mom says how I am like her only boyfriend that has ever done that. I am 16 she is 15. What should I do here, because I don't want to loose her trust?