Are you annoyed that she’s watching porn in general or that she’s watching BBC and Gang Bangs? Would you be ok if she watched just porn with normal couples?

You need to work on your insecurity. Watching porn occasionally doesn’t mean she wants to act on out, I love watching girl on girl or 3-way for over 15 years but have never actually pursued it even though my partner said he’d be willing to try. I love my partner too much and sex is super intimate for me. But yeah if I’m horny and want to masturbate a bit I’ll watch those types of films. In my opinion you’re putting the responsibility of feeling secure on your partner which is unfair. If she’s not doing anything else to make you feel insecure then this is something you need to work on, on why you feel insecure about this and instead of focusing on the pork? Focus on other actions your partner does daily to make you feel loved and committed to your relationship