Is there any way you could take a break from it for a while? The basic things which you need before attempting to hack your OnlyFans account are an active internet connection and knowing the OnlyFans account's username.
I don't yuk anyone's yum, but I can politely decline.
If you see this behaviour as a dealbreaker, tell her that as well.
What if two partners disagree about watching porn? He just feels uncomfortable with it, especially since she lied and broke a promise.
That would be a huge issue for me mostly because she is broke your trust, she promised something which was a lie.