I've had different experiences with porn with my ex and current bf.
I love porn, always have.
My ex watched alot of porn and it upset me mainly because he wasn't interested in sex with me. It seriously affected my self-image and self-worth. It ruined our relationship.
My current boyfriend also likes porn and we watch it together often. The difference is, for him, porn adds to our relationship and romps in the bedroom (or wherever the mood strikes us). Porn is not a substitute for me.
As long as you still show your desire for her, she shouldn't feel insecure or threatened.