You could, but don't deploy her. Having her on the team already buffs all archers on your team. And the video uses Marnie, so you should be good. Marnie specializes in buffing defence and Waltz for attack. I would've used Marnie too, but she was low levelled at the time, so I stuck with Waltz. Anyway, Elizabeth should be able to wipe out most of the undead mobs since she gets an attack boost against the undead, unless that patch has not been implemented yet. If you don't have an advanced tactician, deploy another lightning rod/skeleton on the left side since another lich coming at the 1:40 mark will target your dancer. Alpha's dancer was max levelled and affection, so she was able to survive, but I'm not sure yours can.