I LOVEAnya but only as a nickname for Anna. I hate nicknames as full names, whether they're English nicknames or foreign nicknames. AnnaIsabelle "Anya" would be simply stunning.
I love ANya with its sweet soft sound, but I don't think it fits together with the extremely popular and kind of frilly imo Isabelle (which I also like). The sounds just don't feel compatable.
I prefer just Anna, but Anya is pretty. I'm so entirely over Isabelle, though, so I'm glad it's only the MN. It flows well and is nice, but it doesn't have that spark to me; it's kind of non-memorable.