Masked Marth

I mean... If you want to, then I don't see why you wouldn't. She literally has nothing to fodder except for Iron, Steel, and Silver Sword.

Yep, that's what I did. Literally the only two things you can do with her is merge or send home for feathers.

Merging is definitely the better option of those two IMO.

Yes. When I started the game I chose to fodder her off, regret it a million ways. There's no other use, and it's great because they give you a high merge unit that's great for killing dragons, and can score highly in arena (and I believe is a constant bonus unit in TT now)

I am merging mine.

If you want more dragon checks for Arena Assault, you could give a different blessing to her and not merge them. Because you aren't able to +10 her yet, and seals give bonuses depending on the season, it would be good to keep multiples around.