Smoking Hot Wife but...

I'm not having too much luck getting her to warm up to the idea. She's been with BBC in the past and confided that one of her fantasies was BBC but I don't know how to get her back into it. Her first experience with black was behind my back and it developed into an ongoing thing for awhile. There was a lot of heated arguments when it all came to light, so I turned to the internet to find out more on what motivates women to cheat...duh...should've just looked in the mirror. So, the whole cuckolding thing grew on me. I've expressed my interest in her pursuing her fantasy, but she can't get over the whole guilt thing. Any advice from the ladies on here who may have warmed up to the idea over time (or instantly)? Tried literature, videos, cuckolding memes, you name it. There are times when I think I'm close, but then end up feeling like I'm starting over a few weeks later.