[name_m]Hi[/name_m] Berries! My friend is expecting a little girl in a couple months and really likes the nickname [name_u]Charlie[/name_u] for a girl, but doesn’t want to use [name_f]Charlotte[/name_f] as the full name. What other full names can you think of that would give her the NN of [name_u]Charlie[/name_u]? Thanks!
In [name_m]Stephen[/name_m] [name_m]King[/name_m]'s Firestarter (a book I actually really loved) [name_u]Charlie[/name_u] was short for [name_f]Charlene[/name_f], which almost no one uses anymore. [name_f]Charlize[/name_f] would presumably work as well.
The only one that comes to mind right now is Charleston.
I happen to think Charleston is more for a boy but apparently it’s for girls too.
Other than that, I’d say maybe just use Charlie as the full name. Nothing wrong with that! 
If I think of any more, I’ll come back and edit.
@stripedsocks I do like that suggestion of Charlene!
I second the suggestion of [name_f]Charlize[/name_f]. My cousin is named [name_f]Charlize[/name_f] and is often called [name_u]Charlie[/name_u].
Other possibilities: [name_f]Chara[/name_f], [name_f]Charalyn[/name_f]/[name_f]Charalin[/name_f], [name_f]Charamy[/name_f], [name_f]Chardae[/name_f]. I know most of them don’t have an L but I think [name_u]Charlie[/name_u] could still work as a nn for those names.
I second/third [name_f]Charlize[/name_f]! I knew a little girl called [name_f]Charlize[/name_f] who mainly went by [name_u]Charlie[/name_u] at the daycare I used to work at. Sweetest and most adorable little girl, I have the most positive connotations with both names
Or:
Chalia
[name_f]Cherie[/name_f]
[name_f]Charline[/name_f]
[name_f]Chantelle[/name_f]
[name_f]Chanelle[/name_f]
I’m a [name_f]Charlotte[/name_f] myself and was always very happy with the name. 
But here are some further alternatives:
[name_f]Charlaine[/name_f]
[name_f]Carla[/name_f]
[name_f]Carlotta[/name_f]
[name_f]Scarlet[/name_f]
I agree with @stripedsocks that [name_u]Charlie[/name_u] is a lovely given name on its own as well.
[name_f]Charell[/name_f]
Charielle
Charlin
Chardell
Chariclo
The only names that come to mind are [name_f]Charna[/name_f], [name_f]Charline[/name_f], and [name_f]Charissa[/name_f], but I don’t like them as much as I like [name_f]Charlotte[/name_f]/[name_u]Charlie[/name_u]. The missing L makes it difficult…
Thanks for all your suggestions! I’m passing them on!!