I'm still working on Drink with Me so I'm going to upload this one first.

This song perfectly explains how I interpret Applejack and Spike's relationship. Ever since Applejack's parents died, she has become Apple Bloom's primary guardian. Because Apple Bloom and Spike are around the same age and he's her best friend's assistant, she feels responsibility over him too and considers him a little brother. That's why she's so protective over him in the show. Of course that's just my own interpretation.

P.S. I do not own my little pony or Les Miserables