Who is Ariana Grande?

I had no idea that Little Big Town was going to be performing with another artist until the beginning of the CMA Awards last night.

I heard the announcement about their upcoming performance with this Ariana Grande character, who I think I've heard of.

I eventually watched the performance she did and thought to myself, "oh right, that terrible song that I've skipped by numerous times in the car".

Why in the world did the CMA pick her to perform at the CMAs?   Yes, acts from other genre's have always been invited to the award shows over the years, but why not an artist that might have some resemblance to the country world?  Like Kelly Clarkson for example, who's collaborated with many country acts.

I'm all for the progression of the country music genre and I understand that country today has become more contemporary, but it just seemed VERY out of place.