My best bet would be a mesmer but you have to be able to get 1on1 with her for that to work.
My first thought was to disable Vital Boon with either distracting shot or power block. It might be a bit too difficult, though
Maybe something along the lines of;
Price of failure
Spirit of failure
It's just some random anti-melee skills I could think of. I doubt it'll work, but I think you'll need to think in that direction.