FIrst of all, YES, She is a very sexy looking woman and i cant say i blame you for wanting to have her enjoying Black men ongoing.
I think you need to get to understanding what went wrong with the last time? Was it Him? Her? You, that did something wrong? Was it that one of you missed something? Understanding her mind based on that last experience is crucial.
Ask her fears? Ask her feelings, before, during and after that last encounter. And maybe, just maybe it in some way placed doubts in her mind on the future of your relationship. All things are possible.
Does she know that she was never more sexier to you? Does she know how happy you were, thinking she had amazing sex with him? Or did she not enjoy him as much as the fantasy had her hoping she would.
Lots of questions to learn from.