+Att -Def or -Spd +Def Sing Lance Azura

+Atk Is Rater Good Than -Spd, So i suggest you to merge the second and use the first one

You typically want to keep dancers fast to avoid doubles and keep them alive. Go with +Atk and merge the other, she has no good fodder. Can be good to load up the spare with some C skills before merging, I got a spare instead of Lucy and she's learning a few spurs/hones/drives.

+Atk is generally the better boon, but if you go +Def and also give her swordbreaker you have a dedicatet sword counter, and have more freedom with the rest of your team