This is a scene of Naami being captured by the humans. As said in her bio, her father's herd was ambushed by humans as they invaded the land claiming the mountains. Naami was one of the humans captured, while majority of the herd was able to quickly flee away.
But at night, Naami was bravely able to sneak away and never dared look back or return. She escaped and ran as far as her hooves could take her. Then the next day, that is when she stumbles across Spirit Jr. with Lucky.
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Base: derp8675309 (C), DA.
Naami: Me(C).
Background: Blackhorsebeth(C), Animation Source.