“Yes; but, she is still young and doesn’t realize that Littlefinger has just set her up. “
I wouldn’t count on that; Arya learned much more than how to changes faces in Braavos at The House of Black and White: she appears to be able to astutely read people very quickly. She obviously already has a very deep distrust of Littlefinger,and I suspect she knows Sansa’s ambition is mostly a result of manipulation by Littlefinger.
This is what I’m thinking too.