Littlefinger loves Sansa the way people love their fancy sports cars.
That is all she was to him. A trophy. A living embodiment of how he succesfully rose up in the world and f*ed the lords and ladies of the realm. She was his big f* you to Brenden Stark and Hooster Tully. You can almost see him had he married her laughing at them thinking who is laughing now you two... i married your niece and your granddaughter. She is going to have my kids!!! I win !!!
That is all she was to him. A trophy. That is why he could give her to the Boltons and not bat an eye because it didn’t matter. He would just collect her afterwards like a possession when either Stannis beat them or he and the Knights of the Vale beat them. That was why he could destroy her family and try to destroy her relationship with her sister because her feelings and wants did not matter. All that mattered was that he rise as far as he could to be able to look down on as many people as he could with his trophy by his side.
Disgusting human being and one who was rightfully executed.