Manderlin923:I would definitely use Abigail over just Abbey. Give her some options so she's not stuck with a nn if she doesn't want one as she ages.
This. And I like the spelling - I have a cousin with that NN, spelled that way.
Just throwing in that I know a Katie, Jenny, and Bobby and those are the names on their birth certificates, so I guess in the end you can just do whatever you want to do.