I think
Marnie is a sweet nickname. :-) I think it could probably work for anything with a 'Mar' sound and maybe an 'n' in it, since it's not a popular nn that's already been established for anything else. Names that I thought it could go with included:
MargaretMarianneMarinaMarlenaMarjolaineMarceline
I don't like
Georgie as much but I do like the name
Georgia. As far as full names for
Georgie go, the only ones I could think of were the obvious ones ('
Georg' with whatever feminine ending). :-)