YT!Olivia IVs!

Dancers typically don't engage in battle -Atk isn't too bad on them. +Spd is always preferable to defend against doubles if she does see action and not much, other bows, are likely to take her out in one hit. You can run TA on her so even with the bane she can deal with greens.

Wait what? What does WoM have to do with merging being a good idea? Chill spd is good on her or on certain other units such as firesweepers or desperation weapon wielders.

And I would probably keep +spd, though there's an argument to be made the other way too.

Id also say the + spd. Mine is also +spd - atk and and I have been pleased. I invested in her a bit and gave her firesweep swd and LaD3, and even with the atk bane she still does some good damage when needed.