Versace didn't have many regulars (Isabeli, Raquel, Mariacarla) it was strange, but the collection was pretty fresh and youth oriented so they probably wanted their cast to reflect that. I still think Isabeli and Versace go hand in hand no matter what, but seeing as she's not in Milan, it makes sense. B)
Now if she went to the casting and didn't make it? That would be shocking.