It's more that nobody needs to hear it. It's - very unusual that someone's reason to be an Inmate actually happens here on the ship.

[Or comes to a head here, at least. She's not so unaware of herself as not to realise the seeds were planted long before the Barge, maybe even before Torchwood.]

Most people play their cards closer to their chest, I just...don't have any reason to. That's all.