Well, it's either a skill or an inherent characteristic of higher species like the reborn dragon. Will have to check how the dragon was doing it to compare, but too lazy to go back and check.
At least that confirms that she's not talking out loud... or at least if she thinks she is, she just saying gibberish and we simply have access to her inner thoughts. Honestly didn't give it too much thought on that scene with the spider and the humans, good catch.