Ada isn't a natural nickname for
Adelaide IMHO because the initial A sound is different. Naming her
Adelaide and calling her
Ada is like giving her two different names, to me.
Addie Mona is not nearly as smooth as
Ada Mona, either.
Sue makes a cool middle name for a three-syllable first name. I sort of prefer a longer middle name for
Ada Mona, though -
Ada Susan Mona, sounds like someone famous.
- mirfak