cannot figure out how to tell my colleague to stop signing her initials "af" on emails to immature people born after 1982.

I'm an immature person born after 1982. I giggle every damn time.

@EthanDF Plot twist: she knows what it means and just wants everyone to know she's sincere af.
@EthanDF I'm an immature person born several years before 1982, and it's making me giggle just thinking about it.