She doesn't sound like a Fang, Grip, or Wolf, or even a Garm or Huan. So, how about Princess Mee
from Tolkien's poem by that title found in The Tolkien Reader
and The Adventures of Tom Bombadil
? Also there are a few lines of the poem listed a few posts down the page of This Link
Then again maybe she could be PJ's Lady Arwen
who was quite energetic in his LOTR: Fellowship of the Ring.