Definitely grey. If she was roan or dun, you would expect her head and legs to stay fairly dark, which they do not. If she was brindle, you wouldn't have to tell people to look closely to see her stripes.
Not Brindle.....I say either she is Greying out from a Grulla coat, Grulla, or Grulla roan but not sure on the roan. We have raised lots of roans of many colors and she just has to much white hair throughout her face to be roan....so I say she is greying out from a Grulla coat.