The Stark sisters have a fall out; courtesy, Littlefinger
Petyr Baelish. No one is better than Littlefinger at sensing unresolved conflicts and exploiting it to their benefit. There are so many unresolved issues between the Stark sisters and in seven long years, much has changed between them. Lord Baelish is sure to put his complex mind to play and create a misunderstanding between Sansa and Arya. How else is he going to get closer to Sansa?