I was about to comment on why nobody was trying any healing on mama Eve but they actually addressed that.
That's right, Alice. I knew you're the brains of the family, having won your own fight by relying more on brains rather than just pure magical force. Good job figuring out a solution in this dire situation.
See, the individual fights weren't actually fillers, they were showcases of each girl's ability... and I like how this is consistent with that. Eve won her fight mostly through force with some brain power, Sophia won hers with a balance of brains and power, while Alice won with more brains than power. So it doesn't really feel too weird to me that it's Alice who figured out something here.
The versatility of her weapon is also really only limited by her creativity if her late dad has anything to say about it. So if anyone's gonna do something like this it's gotta be Alice because she has the brains AND the tools to do something about it. She's not up there with Eve or Sophia in raw power, but she makes up for it with things that only she can do.
On a side note, the fight with the late demon king Duke lasting for 3 days is pretty metal. I don't think this dinky bastard king here could stay awake for more than 1. But he's actually putting up a fight against a furious Lloyd, that kinda surprised me since I thought he'd get crushed by now.