I love
Clara. It's one of my favorites. I would definitely go with
Clara! I also like
Matilda, it's elegant and strong. But
Matilde is so common in Italy, I bet she will have to say all of the time 'No, not
Matilde,
Matilda!'.
Viola is nice but I only really love the English pronunciation of VY-o-la (as in
Violet with an A). In Italy it is very overused for babies. I would go with
Clara!