I use her with 4x Noblessse set.
You can either play her with hp/atk/energy rechange/cyro damage/hp (or heal) -- or hp/atk/atk%/cyro damage/crit (or crit damage -- depends on weapon).
Most of her damage comes from using a shield and trowing a ulti just after and then you switch to another dps. Dont even try to dps with her
Oh and btw -- elemental mastery does not work with eula Q explosion as it deals phy. damage. (but it does work with cyro damage on start .. but only if there is a reaction life fischl bird or hu-tao fire dot)
It also last for 12 seconds only so ....(same with noblesse set) its not easy to set up lightfall sword with duraction of 7 seconds due to long starting animation.
Well the hardest part if keeping a mob/boss inside the field for that time. Or to keep them alive