+Atk -Res Olwen

You can make a Quad Olwen with LaD(Swift Sparrow/Fury cheapest) with Desperation. Is actually really strong if you have a Cav partner with her for hone cavalry.
Blade Build is strong too with her thx to her great stat spread.
If you do not want to much inherit cost in her, then still Death Blow is a option too ofc weaker then Reinhardt but faster then him and can still be used in some situations.

Olwen's best build is with a Blade Tome, plain and simple. She doesn't really have the offensive punching power in her base stats to effectively wield Dire Thunder. But she can abuse cavalry buffs to be a pseudo blue Cecilia.

Of course, I wouldn't know first hand as the two Olwens I have are -Atk :(.

My plus atk Olwen. Just love her