I think it's important to point out that Dany didn't sacrifice anyone in the fighting pit, she flew Drogon (and herself) to safety, which is exactly what Jorah, Daario and the rest of her men wanted anyway, for her to live. If she made Drogon stay and fight and keep getting wounded by spears, possibly killed, that would not have been a good outcome. Her presence was the only reason the Harpies were even attacking.