There's a 19th century
Madeline on some branch of my family tree; not a direct ancestor, but a cousin very many times removed. She was always known by her mn, but I do like the less-complicated look of
Madeline.
Madeleine is fine if you're French; no idea what they would use as a nn.
Maddie or even
Mads just do happen, I'm afraid; once people stop being teenagers they seem to shake off the nn and just use the full form. Which I very much prefer.