Send in a party member with 19+ armour (Lae'zel if need be). Then they can only hit her with crits. Add in an imp or a spider if you can.
Use potion of Hill Giant Strength, haste spores, potion of speed, oil of sharpness, etc.
If that ain't enough, Void Bulb them all into a convenient blob and then unleash whatever AOE spells, barrels, Illithid artifacts you have.
I suck at computer games, and I can do it.
So you assume githyanki warriors bonus to hit is +0 or something? She would need to have 27+ in armor, which is impossible in D&D 5, to get hit only on crits.
