Yes. This is a new Meloetta OC. Her name is Nieve. Now, I've thought long and hard about this character. Very long. very hard.
First off, you notice that she has a violin, and that she's blue. These both tie together. First off, She's a Delta species. Ice type. This made her rather pale and well, in this beta art, blue. (Not sure if I want to keep her that way) And a little head cannon idea I thought of was A delta species Legendary, as being more powerful, Gets more effected by the extra type. As such, she is more fragile, like ice.
Now, Relic song is the move that causes Meloetta to change into pirouette form. As such, you must have a quite a bit of vocal power, I would guess, to use the move. But Nieve is really fragile, her voice can't give the raw vocal power needed to change forms on her own. so she plays a violin instead.
She also knows ice beam from her added type.
Her name also does mean "snow"