-attack +def amelia...

Yeah those are kind of unfortunate IVs, I at least got +spd/-atk.

For your amelia I would definitely build on her additional tankiness. Ignis/bonfire was good start, possibly use things like brash assault/quick riposte for follow up attacks to make up for her lower attack and use her bulk.

For her A-slot - Fire boost as you mentioned could be good to bring her attack up. Other options like sturdy blow or fury to boost def and atk at the same time.

Keeping earth boost to make her even tankier for bonus Ignis/bonfire damage and maybe even combine with renewal to make her really hard to kill is another option. Throwing in something like threaten atk if not using armor march to push her survivability and focusing on a battle of attrition, using bonfire/ignis to slowly crush the enemy.

Btw if using BA/QR I would suggest bonfire over ignis for pacing. With her slaying axe, Bonfire will be charged after she attacks and gets hit in return with her follow up attack triggering bonfire and most likely killing her target.

With Brash Assault being better if using her offensively and Quick Riposte defensively.

Edit: While she's kind of like a low hp zephiel with your IVs, her high speed frees up her B-slot of wary fighter and how you use that with the rest of the build will really take advantage of her strengths.

Oh, and other things I considered: with the bit mentioned above fury could always be used if you ever find her being doubled too much or with armor march and an armor buddy with hone armor.

Atk/Def 2 is also a good option for both player and enemy phase if you have it.

Reciprocal Aid with boost skills if not using renewal might be considered. As long as you use something like armor march/guidance in place of pivot and partners who also have a lot of hp(like another armor buddy).

With that much defense, she can tank swordmen. It's pretty cool. I think, just built her with the usual build.

Amelia's BST is so high, any IV set is usuable on her really.