Nyreen is ex-turian military, but, despite this, she is a biotic (turian military hierarchy prohibits biotic powers). Her powers aren't as devastating as Aria's, but she's still useful in combat. Her Biotic Grenade ability does exactly what it says on the tin, and Biotic Protector raises a magic shield, useful for keeping her alive when the chips are down.
Condominas said designing Nyreen was quite a challenge. While a female turian did pop up in one of the Mass Effect comics, there was no video game reference point (and there are female turian soldiers in the game, but they're background soldiers who go unnoticed, apparently).
“We wanted to make sure the first time you see her you realise she's female and not a male turian, so we had to do a bit of work. We changed subtly some shapes to give her a smoother face. I can't wait for the players' feedback!”