I'd just back off.
I wouldn't bother messaging her and wait for her to make contact. How she does so would affect my response.
There really is no excuse for such rudeness. Even if you had (foolishly, IMO) messaged post midnight (which you didn't) and she had kids (she doesn't) and she had been asleep, she could have ignored the message and turned her notifications off or, if determined to reply, just said 'In bed, mate'.
Done.
Just no need for the snark, especially when there's little uniformity in what everyone is doing at 9pm.
Especially now I'm a Celeb has finished 😁
I do agree that it's a bit of a pointless question, though. Most nights my answer would be 'Errrrrr, filling the dishwasher' or similar.
Hardly engaging, interaction wise, and likely to make the recipient feel a tad shit about their boring-ass life, if they're anything like me!
Are you messaging that a lot? Maybe friend had reached a bit of a small-talk saturation point?
Depends on your relationship with the mate in question, I guess. I wouldn't open dialogue with that but if I did I expect I'd likely get back a 'Trying to get these kids to fuck off to bed so I can have some wines. The feckers are doing my head in!' 😆