R.E.N. Spells Ren
Veteran
Why would she be thankful to Littlefinger when it's going to become increasingly obvious he left her with a lunatic....either intentionally, or even worse, because he didn't know?
Fred.
Because she's home, she's ruling, and she got revenge on the people who murdered her mother and brother.
That was intent all along, and he explicitly presented that to her at Moat Cailin. Plus, she's already thankful he got her out of King's Landing and saved her from her crazy Aunt.