Poison dagger Felicia?

Poison Dagger has 5 my and gives the user a 50% total attack boost against infantry only. It's best used on the highest Attack Dagger and that's Kagero and with cavalry and armor units so amazing she's stopped being popular due to relevance being lower. Felicia will still get minimal use out of her dagger and if you want the maid killing people without a charged Glacies/Iceberg then good luck.

Now if you want to make her a debuff Dagger give her Smoke Dagger+. Sets the enemy wan up for death and you can use eithet seal def to doom her first target or windsweep to protect her while attacking distant counter tanks instead. Savage Blow adds chip damage but Atk Smoke is nice as well to help weaken the enemy team even further as well. A skill can be played with some to personal preference based on the iv you have.

I've seen her with one a few times and it does help eliminate squishy mages...it also will make her Iceberg/Glacies a thing of terror for infantry units. However, it's not going to be all that useful against infantry with decent defense without a charged Special or any other movement type.

That said... Take a look at the attached build I encountered in the arena. If you're going for a nuke I think that Seashell+ with QP may actually be her best dagger. This set-up had incredible turn one burst damage (thanks to QP and Infantry Pulse on Seliph).

I did it a while ago, and it payed off.
My 4*+2 Felicia packs an effective 52 Atk with L&D2 and a +1 Seal. Worth mentioning she is also +Atk, so it's even better if she's a *5 (tanks mages a lot better with Fury and can actually take a physical hit).

I keep trying to debunk people that there's quite a feasible way around her low Atk.