An interesting theory. I lean toward the idea that Stripey hasn't killed her yet because she's merely a card in his hand. I don't think the fact that she's a viable source of food for him down the road is factoring into any equation, neither do I subscribe to the idea that he's worried about losing soldiers. If that was true then there would have been no attacks on either The Tower, the Mallers or the other tower. No, it strikes me that if she is still alive it's because she's either lucky or she's serving as bait--unwittingly, of course--for a larger prize.

Good thought though.