I don't think porn is cheating either. The only time I'd get upset with porn is if it was interfering with our intimacy. If your "taking care of things" by watching porn, and then couldn't be intimate with me, THEN I'd get upset!
Otherwise, what's the problem??
Will she watch it with you, or is she totally put off by it? If she won't watch it with you, then just make sure you do it when she's not around. Otherwise, I don't see where there would be a problem. As long as you're open and honest with her, she shouldn't have a problem, but you're certainly NOT cheating!
Try and talk with her about this. Why not show her our responses. Maybe that will help her understand a little bit more. God bless and please take care. Hugs, Lee