I think you need an equally beautiful, long, flowing middle name to compliment a gorgeous name like Arianna!
Ariana Elexia is sooo pretty! It has that "wow factor"!
I also like Ariana Kaylin, but not as much!
Marie, in my opinion, is way too bland & ordinary (30 years ago it seems like 75% of all babies were given the middle name Marie or Ann -- as common as Mae, Rose, & Grace are currently)
Some additional suggestions:
Ariana Sophia
Ariana Jasmine
Ariana Elaina
Ariana Paige
Ariana Sapphire
Ariana Mariah
Ariana Juliett
Ariana Kiara
Ariana Sierra