She looks great for 24! I have seen a lot of standardbreds that seem to be hard to keep weight on, but she looks great! I would worry a bit about the cresty neck, maybe look into cushings like someone above suggested? Otherwise if she is happy and pasture sound (you mentioned she was retired) she looks great! Nice strong hindquarters, a bit of a hatchet neck, but nothing scary!
What did you do with her before you retired her?