You use this word to a younger brother or Sister.
"Nerd" for being unpopular and weird, and "lette" metioning that they are young. so in other words, a wierd young one.It's no word to take offense to, it just is a word brothers/sisters used to call there younger siblings to mess around.
little brother:Can i use your cellphone suzie?
Big sister: No.
Big sister:No Nerdlette!
Nerdlette: A common name for girls who don't like being call 'Nerds' because it sounds manly.
It's mostly used with a group of girls. Men mostly take offense when being called a Nerdlette.
Boy 1- "See that group of girls?"
Boy 2- "They are the Nerdlettes"
Boy 1- "Ah, Nerds"
Boy 2- "No bro, Nerdlettes"