I really like
Eira, too.
Ay-rah, and Eye-rah, I usually how I've known it to be pronounced. I like Eye-rah, personally.
I think it is very usable on a child. I'd probably give her a more classic middle name though.
Eira CatherineEira FelicityEira CarolineEira IsabelleEira NathalieEira PenelopeEira CharlotteEira Margaret