Can Ada be a nn for Adalee?

[name_f]Adalee[/name_f] is pronounced [name_f]Adda[/name_f]-[name_u]Lee[/name_u]
[name_f]Ada[/name_f] is Ay-Duh

Absolutely, [name_f]Ada[/name_f] is in the name so despite the differences it can definitely be a nickname.

I would use [name_f]Ada[/name_f].

Yeah for sure!

Yes, no question.