Because you asked your daughter about her color preference and she answered clearly, I think you should go with the black/gray/yellow. Those who've already responded have given you wonderful ideas for doing this.
As you probably know, the black/gray/yellow scheme has been VERY popular for weddings the past several years. In time, the combination will become passé and the quilt will look "dated". But at least it will reflect the time of her wedding, rather than someone else's. And whatever else, she requested the colors.