Shes gorgeous!
Im not a breeder, but shes definitely a dutch. Shes probably puredutch, just with non-showable markings. I dont know if youve had a lookat some of the other bunnies on the site, but MyBoyHarper has a dutchboy (Harper) who is pure dutch, but his color comes up to the neck theway Thumper's does. (Ideally, that white part should meet the darkercolor around the midsection).
Shes gorgeous though!