I had this same problem with black horses. They are nearly impossible to get a good picture of them. I found that overcast days were the best for them. Diffused light works best. Yogi has a very dark face and it's often hard to get his eyes to show up in pictures. I find that good overhead lighting and no flash work best for him.
Outdoor, cloudy day, no flash
Indoor poor light with flash
Indoor good light overhead, no flash
Try to keep your background as clear of clutter as possible and have the whole area around brightly lit. But not necessarily have the light directed straight at her. Good luck!