Note: While you could test your out-of-office message, you can also see it’s working because Gmail conveniently overlays a yellow bar at the top of your inbox reminding you that your autoresponder is on, along with options to “End now” or adjust your settings.
That sounds like she’s using an auto-responder, not an Out of Office. The primary difference, as far as I can tell, is that an auto-response will respond to every email, whereas the OOO message will only reply once per sender when it’s turned on. (Turning it off and then back on resets it)

Humorous Vacation Message. While you shouldn’t use a vacation message like the first example in this article, it doesn’t mean you can’t have a little bit of fun with your emails.
What we need in our work communication is not more professional politeness or less formal, chat-based messaging applications like Slack. We need honesty. The problem is that we’ve conditioned ourselves to see honesty as self-indulgent or disrespectful. I’d argue the opposite is true. Honesty, even if it’s a bit more inconvenient for all parties in the moment, pays dividends later. It builds trust. When my partner Anne Helen Petersen and I were interviewing people for our forthcoming book on remote work, a frequent lament from both middle managers and workers was that they didn’t feel like they knew how to succeed in their jobs; that they were guessing what their superiors and coworkers wanted and, even when they asked, they didn’t quite trust the responses they got back.