Marnie - I love
Marnie. It's so cute. I'd love to see a little girl called
Marnie.
Marni - This looks incomplete to me. I don't like this spelling at all.
Marna - Don't really like this. I think it could be good to use
Marna with the nn
Marnie because
Marna sounds more mature. I don't like
Marna that much though.