Miley's original name was Destiny Hope Cyrus. But her dad called her Smiley Miley. So it caught on and it became her real name. ^_^

Yes, It was a real name before Mylie Cyrus. I know someone who is in their 30's with the name "Mylie"
But, She is the only other person I've heard of with the name "Mylie"

I think its probably made up cuz that was the first time I heard of it.