Is my -atk +def Ayra salvageable?

Yes because it’s ayra. Her special is busted.

With +Def, she could get into desperation range safer in doing combat. She may need some atk buff with support but as long as she can double and in desperation range, she should do quite well in a variety of situations.

Yep, as long as her speed isn't the bane Ayra can still hit like a truck with Regnal Astra. The Def boon also improves her standing as an Enemy-phase style character.