Being just the worst at not accruing fresh curses, Sam dismounts to stretch her legs, and plucks an apple from the tree. It looks safe enough, so she wastes no time in eating it, and even has a couple more. She is trying to make a meal out of apples after all. By the fourth she isn't even bothering to pluck it first, she just cranes her long neck out, reaches forward with her snout, and bites it right off the tree, before returning all four of her hooves to the ground.
Wait.
Sam stares at the ground for a moment in contemplation. "I just ate a bunch of cursed apples and got turned into a horse, didn't I." she thought to herself. She didn't have long to ponder how yes, that was very clearly what she had done though, as seeing a beautiful mare nearby got Cinnamon into a bit of a mood, and he wasted very little time in trying to mount her.
Horrified, Sam kicked him away and tried to distance herself, but he was very persistent. It was a true battle of wills. A battle, of strength.