What I'm being told in genetics is that a dorsal stripe means a dun, not a buckskin. However, if she's shedding out light on her muzzle, and she has black points, legs, mane and tail it sure sounds like it doesn't it?
In the picture she looks like a dark bay or a brown. UC Davis will do color testing on horses - I've thought about having one or two of mine tested. Then I think, just where am I going to get the dollars for this :)
I think she looks like the dark bay coloring that is very common in warmbloods, and they sometimes have the lighter muzzle rather than the dark. She's really very beautiful.