She announced she was leaving the office (as in, leaving work), from somewhere outside the office.
No longer at work equals "left the office" whether or not she was present in that physical room anytime she was at work.
Maybe she was promoted - but the promotion happened in a different room, so she has left the office that day (left work), without having been in that physical office... yet. Or maybe her office changed rooms that day, so she left work (her old office) without having been in her new office, ever. Maybe she had on official office, but really always telecommuted (and so never actually entered), and has announced she's left the office (is off the clock, or quit) without having been in that room.
Maybe she quit or stepped down, and so "left the office" of her boss-ship, without having "entered" it ("entered" is not how we usually speak of gaining a promotion, so maybe it's just a word-pairing mismatch. Or maybe she left it just not having been in the office-room).
Alternate theory - she was talking to someone via the computer (skype/telecommute/etc) and someone didn't end the call before carrying a device she was speaking on, out of the (physical) office room - she, through her call and the computer in question, has "left the office", has been carried out - but didn't "enter" because the call wasn't on yet (calling into a room is not considered entering).