I love the name
Margaret! I think it's classical and beautiful. I don't however like
Maggie for a nickname. To me
Maggie sounds childish and makes me think of a shy and insecure young girl. Personally, I'd try to keep
Margaret as is and not allow it to be shortened. But as for nicknames, I think
Daisy is the best. Most people don't associate
Daisy with
Margaret though, so that may be difficult.
Gretel is nice, if you don't mind the more foreign sound. Of the commond nicknames, I most prefer
Meg. I think
Meg is very sweet.