Millie

Millie is one of Yor Forger's three co-workers at Berlint City Hall. Millie is shown to be lively and mischievous, suggesting to Yor that they put snot in the Chief's coffee as a joke and most often seen smiling or giggling. Even though she breaks up with her boyfriend, she doesn't seem bothered and remains cheerful, even asking Yor to introduce her to Yuri.

(Source: Spy x Family Wiki)