I wouldn't be at all afraid to breed her. I have bred maidens older than that. Just have a vet check her for breeding soundness. If your looking for a dressage or eventing mount I would look at Warmbloods who cross well with TB's. Also check out the Warmblood registries that still accept TB mares and pick an approved stallion from them. That way you can get your baby registered. A stallion with some jumping blood can help you with the eventing part. Just take a very objective look at your mares strengths and weaknesses so you don't compound them. Breeding is fun and have fun trying to decide on a daddy if you do decide to breed. What a adventure.