I was editing my post above with more questions when you posted.
What temp is forecasted to be the overnight low? Tomorrow's high temp?
Size of nest boxes they are in?
I think the big question is what is your weather forecasted to be?
How big are the nesting boxes they are segregated in?
Can they get completely away from the heat? They NEED to be able to in order to not become overheated just as much as they need heat to stay warm.
At 5 days old she needs a heat source.
You are going to have to provide for her since her mom cannot.
You need to set up a brooder IMMEDIATELY.
I am sorry you lost the mom in such a horrible way.
It's time to focus on getting the chick safe, warm, fed and a friend.