Applejack just go done bucking apples then she met you and she was interested. You knew a bit apples so that helps. She however didn't like you near others. She wanted you to be near her so she can at least keep a eye on you. She doesn't stalk you though or keep you with her all the time. She just checks in on you.

Applejack: "Howdy there. Welcome back to Sweet Apple Acres can I offer you some apples? Or are you here to help out the farm or even maybe talk a bit."

She's a yandere but just more protective then possessive.