Should I sacrifice my only Nephenee to Hector?

Hector(LA) is arguably the best user of Wrath at the moment, primarily because Berserk Armads and Wrath itself stacks together.

If you use Bonfire as your special, Berserk Armads naturally reduces its CD by 1. Assuming you bait with QR3 seal, you will proc the first bonfire on your second counterattack, which will most likely kill the first bait & leave you either healthy enough for another bait or leave you at Wrath range.

Once you hit the 75% HP threshold you gain a 2 CD reduction at the start of the turn, meaning you can fire another bonfire +20 dmg immediately (40 dmg for neutral unmerged), which will most likely let you kill anything even at a triangle disadvantage.

A double Wrath Hector would certainly be powerful but Nephenee is an excellent unit and one I would suggest keeping. She's my go to bulky lance (+Spd -Res) with defense refined Slaying Lance and Fury 3 her stats are 42 HP, 48 Att, 41 Spd, 41 Def and 20 Res. Very quick, very physically bulky and, for me certainly, very useful. And as you say, her design is magnificent.

Hector has other options, you have only one Nephenee.

Gimmicky but not necessary to run double wrath on Hector to make him a success. I wouldn't fodder off your only Nephenee for that, especially if you do find a use for her from time to time.

I am T18 and was fortunate enough to pull a +atk Hector the other day and one thing I have noticed is that bold fighter makes him one round most units in the game and is even better than double wrath+ QP.

If you have a Lissa you can fodder off for bold fighter I recommend that, and use your seal slot for QR3

Be happy with your LA! Hector. I regret building my +atk/-res one and wish I gave that Bold Fighter and Armor March to my +res/-spd one.

That said, LA! Hector doesn't need double Wrath. He decimates everything as he is. Damn, he one-shot Infernal Navarre for me today...