She can indeed go into full defense and take that move. I'll assume Rashak moves to C3 to stay within the glaive-wielder's range and maintain cover from the scythe (due to the table).
Rashak and Ellena both attack the cultists with all their might, but they are still trying to react to the situation, and the attacks go wide. Rashak withdraws to give Lyddy an opening, but she finds that she can't move forward as much as she needs to to reach the slowly-dying Horgus.
The two cultists exchange glances, clearly uncertain about this new turn of events, but the scythe-wielder can't spare much attention from Ellena. She takes another swing with the vicious weapon, shouting at the top of her lungs, "May the Lord of Locusts devour you!"
Scythe attack: 1d20 + 5 ⇒ (13) + 5 = 18, damage 2d4 + 3 ⇒ (3, 4) + 3 = 10
Unable to turn his weapon to the same use, the glaive-wielder takes a moment of concentration while holding a defensive pose. Concentration check: 1d20 + 8 ⇒ (4) + 8 = 12 Unfortunately for him, he cannot manage to focus well enough to channel his demonic patron's power, and nothing seems to happen.
You guys are all up now. Here's the new map.