Yes, Alanna, you have the right instincts, I can see. Wow, my Runner girls play hop on top but no one has gotten hurt. Some ducks are just more aggressive, I think.
Yes, get her separated - sometimes just a temporary divider fence can work well.
I find that the @naivetefarm tagging does...
@naivetefarm - Hi!
I am with Miss Lydia. Really sounds like she is getting abused by drakes. So please, get her away from drakes a.s.a.p. for her health's sake and her life's sake - yes, it can be that serious.
Then take a breath and begin to sort out how to adjust the flock dynamic...