Yay Riposte!
I'll roll the three concentration saves here. The DC should only be 10. If she fails any of them then Bane is cancelled.
(1d20+5)[14]
(1d20+5)[9]
(1d20+5)[12]
Welp, no more Bane. While she failed the second con save, meaning the leader of the knights was not affected by Bane, his first hit would have missed regardless so Nith still gets to riposte against it. I don't know if that affects the rest of his turn for you, unless he fails his will save and ends up with disadvantage on attacks?