From your list, I like [name_f]Gwen[/name_f] best.
More suggestions:
[name_f]Pearl[/name_f]
[name_f]Rosemary[/name_f]
[name_u]Hazel[/name_u]
[name_f]Sadie[/name_f]
[name_u]Ruby[/name_u]
[name_f]Iris[/name_f]
[name_f]Olive[/name_f]
[name_f]Mae[/name_f]
[name_f]Flora[/name_f]
[name_f]Ada[/name_f]
[name_f]Belle[/name_f]
[name_f]Opal[/name_f]
[name_u]Cleo[/name_u]
[name_f]Mabel[/name_f]