Halibut — Food safety facts
Safe to share · Dogs · full breakdown on the linked food page
Safe cooked and plain in small amounts.
Short answer
Yes, a small amount of plain, cooked halibut is safe for a dog on heart medication. It's a lean protein, but you must ensure it's free of all seasonings, oils, and bones. Offer a bite-sized piece as a rare treat, and monitor for any digestive upset or changes in her condition. If you notice anything unusual, contact your veterinarian.