It's not her job to help him with his porn habit anymore than it would be her job to help him if an alcohol addiction was interfering with his sex drive. All she needs to do is signal "I will not stay in a sexless marriage" and he can decide if he'd rather be alone with his porn. She could also tell him what a big turn-off it is for her to be married to someone with that kind of habit. I mean, think about it, would most women choose to date a guy whose profile said something like "One of my favorite hobbies is jacking-off to images of young Asian women doing unspeakable things with tropical produce." Highly doubtful.
"Tell me, what is it you plan to do with your one wild and precious life?" - Mary Oliver
