Stop hating on Sansa, I think it's totally in keeping with the story that she's turned into a schemer like most of her elders were. She could be the next generation Cercei, which we need because too many of these GoT millennials are leaning towards making a better world and shit. Sansa's transformation is what makes this series great.
To be fair, after all she was put through, it's seems pretty reasonable for her to harden rather dramatically. She's earned that right.
To your point about Ramsey knowing they were on the way: her own brother and allies didn't know they were coming, so give her and Littlefinger credit for running a special op.