L&D or Darting blow

It's really dependent on team composition, but from the looks of it, your Caeda doesn't have the most defense, so she really shouldn't be taking damage from melee units if you want to run L&D3. If you want her to survive melee attacks, then I'd recommend switching to Fury (in my opinion Darting Blow isn't really worth it unless you're running her in a team that doesn't have Hone Fliers, and even then Fury is arguably better, just switch her seal to one that increases her speed probably.

You can always run Fury. Then she could use ploys and Iceberg/Glacies more effectively too

Ideally she wants an atk boon with an hp bane because weapon refine will patch it up. She gets tons of speed in flier emblem so she would just need the damage to compliment it. LnD hurts her bulk significantly and cannot safely get into desperation range. Fury is much much better on her and can get you into desperation range safely while giving her extra stats that pretty much matter to her. Once she's in desperation range, she can sweep most threats, especially against armor and cavalry.