Also, sometimes - not in this case, to be clear - "it's a joke" can be part of the problem. The fact that you (again, not you, Nick, a general you) think making crude rape jokes is a-ok and telling a woman to shut up and bend over is funny, is actual rape culture at work...at work.
Which doesn't mean I think rape jokes are evil, on the contrary, I'm a firm believer in the idea that you should be able to joke about anything...but not every joke is appropriate in every context, and some jokes are very prone to being misread. Heck, I've had more than a few discussions inv this very forum about things I said in jest that were misconstrued and/or interpreted differently than intended. Sometimes, I've put it down to " X was in a bad place/looking for a fight", sometimes I've looked back and realized "yeah, that was the absolute wrong thing to say" or "wow, what the F was I thinking". I've actually learned a few things about how or when what jokes are okay from this place.
That said, in this context, I think it was possible to make a joke about it, but "too slow! Haha!" probably came off as derisive, mocking her for not having seen the other response or being too slow at her work, while she was trying to be helpful. Personally, I'd probably have made a sarcastic "thanks, I'll let me from an hour ago know" or "wow, thanks for being so much more precise and in-depth in your reply than Y" (bonus points if they both really gave the exact same reply) joke out of it, both of which would probably have been worse than what you said.
