Here’s another idea:

When D’Arcy is updating the crew about what has happened, after she says all their leadership except for Leia is gone, the crew moans and groans a little. During this time, we could add a new voice line or two from random crew members asking questions like:

“How did they find us?”
“There must be a spy!”
“What are we going to do?”

Then cut back to D’Arcy, continuing with, “To that end, the chain of command is clear…”

At the very least, something like this can illustrate that the Resistance fear that there might be a spy leaking information to the First Order. Now, Holdo is going to take charge and handle the situation.

Instead of Holdo explicitly mentioning a spy, we might be able to piece together a line like, “The plan, is need to know” or “It’s a need to know plan.” I’m pretty sure she says these words in some shape or from in this scene and throughout the movie, so maybe we could get something that sounds passable. This would also work well because later, when 3PO suggests to Poe that they tell Holdo about their plan, he says, “It’s a need to know plan, and she doesn’t.” So that might help him seem impetuous.

When Leia speaks to Poe, maybe she could just say something like, “Holdo was protecting the light.” You could piece this together from that sentence she says. While it isn’t as clear as what you were suggesting, it might at least remind the audience that she was just trying to protect the Resistance by being cautious about the plan.