from what I could tell Lyn rocks the carriage to the side from her position on top, forcing the witch to stop the carriage (the horses seem to be magical too). Then when Renald and the knights catch up, the witch walks out of the carriage with a knife/dagger to the prince's neck. So the confrontation happens. Prince Isaac grabs the dagger, wounding himself(?). The others start to charge, but the witch activates her powers and brings them to their knees.
Lyn, after some inner thoughts/planning I think, jumps down onto the witch's back and the witch's magical disguise wears off. She's actually a really old lady, like eww haha.
And so epic battle commences and Lyn joins the battle.
And at the very last page, Prince and Lyn cuts the witch down the middle of her face up to her chest.