You should try and talk to her about this. I am in a relationship, and my boyfriend watches porn openly. Sometimes we even watch it together. I know that a lot of people are really bothered by porn, but I don't think it should be considered as cheating.

I can understand why she is upset if she was of the understanding that you do not use porn, and then found out you do. Its a trust thing. So try and be open and honest with her about how you feel about all of this, and what porn is to you. It sounds like you really care for her, and porn shouldn't have to be the ruin of your relationship if you really love eachother. Good luck