and there's the problem. instead of working with you to come up with some sort of compromise for a good sex life within your marriage, she basically told you to jerk off to this woman and "keep her off the hook".
Never mind what you're doing, worry about the fact that she's ALLOWING you to do it. That's telling of your marriage, right there, as well as her true feelings for you.
Years and years ago, my ex wife blindsided me by saying I can go get oral sex from other women - and she meant it. There was nothing "trappy" about it. (long story, but she had TMJ, jaw issues, and could not perform oral sex on me. I literally never even complained about it. So I was not sure where it even came from).
Well, guess what? This was during the beginning part of her affair, which eventually ended our marriage. At the time, I had no idea of course, but in retrospect, the timelines matched up well. It came at a time where she no longer gave a crap about such things, even though we were still having sex. But when you disconnect from somebody, as she did, there is no longer even a tiny bit of jealousy - she just didn't care. It was also some sort of justification for what she was embarking on.
I am not AT ALL suggesting OP's wife is having an affair, but she HAS disconnected from him.