Elizabeth hears what isn't said.

This young girl was already caught up in something terrifying before she ended up in this vault underground. She was running. She can see the way she shudders. The world can feel like it's caving in.

"I'm afraid it is real. At least you don't have to run." She winces. "For now."

They have no way of knowing the dangers of this vault. She won't lie about the reality of the situation to protect someone even to someone so young. Besides the girl's smart enough to recognize the danger in this place.