For those that actually followed the show, with some semblance of an open mind, the reasons were actually quite clear.
Sansa's dialogue with Jon, made it quite clear why she choose the path she did. She asked Jon, why she wasn't included in the meeting, she being the one that knew Ramsey the best. She warned Jon, that Ramsey doesn't fall into traps, he sets them. So Sansa one upped Ramsey and set her own.
Sure, Sansa could have shared with Jon the coming of the Vale forces, Jon could have waited a day or two, and then what? Ramsey, seeing Jon had a much more formidable force would have remained inside Winterfell, and we would have had a two year long siege battle. D&D actually gave a pretty good reason why Sansa didn't share.
I gave the episode a 9. Pitty the spoilers were out there, that is the one thing that hurt this episode. For once, for the first time this entire season, the writers gave Peter Dinklage some dialect he could actually do something with. I like the Mereen scene, but it was a bit too rushed. The all of a sudden appearance of theon and yara didn't make any sense, but the exchange was good.
We now have women in power almost everywhere on the map, with the exception of the Frey's, and the imminent over throw of Euron.