Help my bride out! Attack or Speed?

If so, then +spd-def. Once she hits desperation range, she'll want to nuke everyone and as such, simply lowering her weak def a bit more wont be the end of the world. She'll be able to drop into Desp range by fighting mages.

If you want to play safe, keep +spd because spd will continue to powercreep. I generally find that she's already so fast I tend to go for +atk, but then again, she also hits really hard already so both are good options.