この間も『のりこくん、お弁当買いに行ってくれないか』だって。
I know that the suffix くん is used with boys' names, while ちゃん is used with girls' names. But I've just listened to a dialogue between two girls, and one of them is talking about what her boss said to her.
Why is くん, not ちゃん, used with the girl's name？
one of them is talking about what her boss said to her.
This is very important context. くん can be used by a boss for a subordinate regardless of their gender. Outside of workplace, it can also be used in other hierarchical settings, e.g. a teacher talking to a student or a school club's president speaking to a club member.
However, as mentioned by @naruto, especially in workplace it seems to be going out of fashion, in part exactly due to the potential confusion about the person's gender. The gender-neutral さん is likely the better option nowadays.
