I assume she was in her Slayer form?
Because I also lost the duel during my blind Honour run (wanted to beat her honourably as a Slayer myself), but I can't say her original form with 12 stacks posed much of an issue after things escalated.
She ended up disarmed and then tripped on the floor flopping like a fish while paralyzed as my physical party just kept smacking away at her through the stacks, even got the achievement not to kill any ritualists. Kinda humiliating and anticlimactic

Surprisingly she is very easy to crowd-control, especially paralysis or disarm. I think she is equally susceptible to crowd-control in her Slayer form.