You need to ask if she considers a darker tan or a light brown in her spectrum of neutrals. I would definitely not consider those colors with the information you gave. Light neutrals and darker neutrals are different animals. Both are attractive but are definitely different and you need to know what she is thinking. If she is ok with the contrast that darker neutrals present then that will make one kind of quilt. If she wants a neutral quilt that has very light color variations that are almost shadows of each other, almost like the nap differences in velvet then that is another type of quilt altogether. I think that you need to get more specific information from her. It would be a shame to make a quilt based on what you think she wants instead of what she actually has visualized receiving from you. The more specific information you receive the empowered you become.