How to build yt! Olivia - spd + hp

Depends on how you want to use her. I pulled her -SPD/+ATK during her banner and have set her up as a pure support.

Mine is built as follows:
A - R Duel Flying 3 (Used Fury 3 until I got a Laegjarn to fodder for this, if you don't care about Arena score use Fury 3)
B- Chill SPD 3 (Wings of Mercy 3 is also great here if you're using her as pure support)
C - Guidance
Seal - Drive ATK (Alternatively Iote's Shield if you're using Drive ATK elsewhere or are tired of her getting ganked by bow users)

Personally, I put her on a team with three armors and let her dance them around the map. I don't let her enter combat unless it's unavoidable or she has triangle advantage.

One option is base kit until you pull a better IV, and then fodder chill spd or bracing stance to someone. Generally speaking, I think the base kit is fine; fury is maybe slightly better to make her extra hard to one-round.