Hmm. Even larger, faster dragons in her canon aren't portrayed as that fast. Let's go with flying 8-10 dft per day. She ought to be slower than Julien, and markedly slower than the max.

Miki's non-essential! Without Lleld she'd mope and stay near the normal animals to herd and protect them. It's possible she'd pick someone else to be her rider, but unlikely. In general she'd have less interaction with people than Hawke's dog. Llysanyins tend to stay near their stables and pastures when they're not on the road, letting their people do more complicated people things.