is exsesive masterbating to porn sites healthy in a relationship that is already very sexually satisfing?

finding porn sites to masterbate to? our sex life is great and frequent. my partner shares and performs masterbatoin when were together. but i feel i can't trust her when i'm at work. she knows this bothers me alot as our sex life is very satisfing. by the way my partner is an addict, 15yrs clean but still has the attitudes and behaviors of one. she feels that now i make her feel guilty about her masterbating and now lies to me about doing it.
she has moved on to other porn sites and it took her a week to tell me about them. she claims she just diden't get around to it.
is this normal?
we have sex often and she masterbates just as often!
please help.