I don't know what to do with Cordelia.

I personally prefer Firesweep since it doesn't detract from her speed, and Firesweep is more powerful. Not only that, but if she doesn't kill an enemy while using Brave Lance, then she has to worry about the enemy retaliating, and, in my cases, I don't want that.

I used the same IV’s until just recently (switched to +Spd/-Hp) and she still worked beautifully with the firesweep set I gave her with Galeforce/Heavy Blade combo

For a +atk, go with Brave Lance.

Definitely Firesweep. I even gave my +4 Cordelia Swift Sparrow for her quad build and still prefer Firesweep.

When I barely make T20 I use Quad for higher scoring; for regular use I nearly always use Firesweep+Hit and Run.