I love
Helen and would use it willingly. I also like
Eleanor and
Elinor, about equally. I dislike
Ellen,
Elaine and all the
Helene and
Helena variants. I don't think
Helen needs a diminutive.
Susan has never appealed to me.
Susannah is a family name, which I'd use happily enough as a mn. If I had to use a form of the name, it would be
Suzanne, with a respectful nod to
Leonard Cohen! I also quite enjoy
Suzette. As a diminutive, I prefer
Susie to
Sue; I don't think
Suzanne needs to shorten. I taught a
Suzanne once who tried everything she could to make people call her Zanne. Her peers called her
Suzanne, so did most adults, and I called her
Suze. Now she's grown up and is cheerfully
Suzanne.