Speed is a nice boon to have, but if you don't want to her defense to be even lower than it already is, then +Atk/-Res is also a nice choice since her resistance is already not that important.
I'd say +Atk, with Fury and a speed refine on her lance she'll hit 44 speed before buffs which I think is plenty while the attack boon puts her to 52 with Fury.
Pokemon GO
Fire Emblem Heroes
Fate Grand Order
Dragonball Legends
Dragalia Lost
IV Calc
Heroes