Well whoever said the horse wasnt built right shouldn't be allowed to post anything on here. She's a little long in the face and her neck is a little thick, but She will probably grow into both. She has a solid pedigree, but really any horse can be a reiner if they have the drive, heart and training to back them up. I dont think you would be making a bad decision to try the filly. And if she doesnt work, then sell her for a local show pony or a trail horse! She's just a weanling and only time and training can tell when they are that young.