A Liver Chestnut Roan (or sabino instead of roan)
A Smutty Dun Sabino or roan (does she have stripes on her legs?)
A Smutty Buckskin Sabino or roan
A Silver Mahogany Bay roan (with not a lot of white in the mane and tail)
I personally would go with a Smutty Dun Sabino. That's what I think she looks most like lol.