Would that make my character a "Mary Sue" type?

So I posted a question previously asking for an animal idea. My character needed an animal to ride. The terrain would be tough, as she and her comrade were attempting to avoid main roads. I didn't think a horse would be a good idea. And, as the theme of the book is the regeneration of dragons, a dragon as a steed was obviously out. I also didn't want anything with wings. But there was a person who accused my character of being a "Mary Sue" type because I didn't want to use a horse...I think I've finally settled on an elk. So I was just wondering, would that make her, "Mary Sue"ish?