The background is from the movie Spirit: Stallion of the Cimarron.
It can be found here: http://www.yorikoito.com/wp-content/uploads/2013/09/032-019-finalprint.jpg
Character (c) Me
Completely coincidence.
While they are similar, there's plenty of differences. Their fur color is different shades of gray, and the design is different around the eyes, hind legs, and tail.
It doesn't bothering me at all with people making comparisons to other characters. This design style is pretty common, and I've seen many characters with similar designs.
Link
Lunawolf
For a second I thought this was https://www.weasyl.com/character/44604/ellie-wind