The only thing that she — and more importantly, Littlefinger — need to understand that is that Jon was going to fall for Ramsay’s trap, and was likely to be on the losing end of things. That would mean that at some point, Ramsay would expose his flanks, both tactically and emotionally because Ramsay will want to…

Because Jon was going to be Jon and allow honor and emotion overcome cold hard strategy, just like their father.

I’ve been reading a lot of comments wondering why Sansa didn’t tell Jon about the Knights of the Vale coming (assuming she knew for a fact they were). I think there were several potential problems with telling Jon. For one thing Jon hates Littlefinger, and probably would tell her to send the army away again. Even if…