She looks in great shape for her age and history - nice and clean-legged, with no blemishes. Unusual for a SB that's raced for a couple of years.
She has a lot of knee action in front at the trot; perhaps you can work with your farrier and her shoeing to help that.
IMO, the biggest challenge in working with a STB off the track is teaching them to bend undersaddle. They're quite sure that if they do, they'll get poked by a cart shaft. Working with her on the ground and asking her to yield her shoulders, barrel and hindquarters separately will help, but do be prepared to spend a lot of time on bending correctly once she's under saddle.