The Princess is better at withholding information than she lets on - many of the pieces of information she gives out have little practical use, but it gives everyone a win and lets her enjoy herself to boot.
...except she's constantly giving out actually-important information - one of the first things she spills is the army's troop formations. She's just lucky.
That... doesn't actually disprove it, really. While she has roughly zero experience at being a person, she has extensive training as a soldier, being raised from childhood as a living weapon... more Ex's handle than anything else. As a result, she most likely has a lot of skill at reading situations and enemies, since this would be invaluable for, e.g., preventing sneak attacks by traitors. She may very well have realised that revealing that secret right at that time would ultimately not harm her people, and thus used it as a way to test her captors, to see what they would do. It's also possible that she might just be enjoying herself enough that at least on some level, she's fine with revealing potentially dangerous information just to continue what may well be the first vacation she's had in her entire life, and the first time she's actually been treated like a person. ...Or maybe she was able to suss out that her captors are more interested in peace than victory, who knows.
Torture Tortura actually chooses her "tortures" carefully: she knows she's dealing with people who would easily resist normal tortures and temptations... But are completely helpless with the completely mundane offerings she givesl, to the point she successfully got out secrets from the Hell Lord and even Ex, a sword.
The Hell Horde torture exam from lieutorment to harm-marshall consists in torturing the Hell Lord and get a secret out of him. That's why Maomao is a harm-marshall at her young age: the Hell Lord would never succeed in keeping anything from her.
Fridge Logic
So if Enki and Youki aren't sisters, which one of them is Inosuke's sibling?
