Sovereign Rune

[Ujitsuna]

The Sovereign Rune would be useless to her, she needs to use her magic, and the hydra doesn't count, mainly because it's for gameplay purposes (you need to have some huge monster to fight at the end) and she wouldn't be able to use her Gate Rune magic as the hydra either.

[AA]

I am doubtful that Windy even knew about the Rune, it was attached to the hilt of a sword that had been the property of the royal family of the Scarlet Moon Empire for generations, i'm sure that they didn't run around telling everyone about it.

The only ones outside of SME that would know would be people in Harmonia, and since Windy isn't on the best of terms with them i don't think she would find out from there.

She wanted the Soul Eater, no other rune and surly not the whole 27, she wanted the power of life and death since she felt it would suit her and her plight against Harmonia, which was her true goal, the reason she stayed by Barbarossa side was because she would need the army of SME to even stand a chance against Harmonia.

Although to look at the Sovereign Runes powers having it might actually aid her at some points, say if a Harmonia sends out the clones (assuming there are more than two) all with highly powerful magic runes.