Everybody else will act normal and all prior evidence of their existence will also persist like normal.
I guess for most people it would be pretty much immediately if their significant other isn’t there in the morning and for some fringe isolated cases it might take forever.
I guess best case for me would be around 4 hours on a work day during lunch break seeing a big crowd of people when it would finally click.
Worst case would be probably 5 days when I’m mostly working from home office.
Immediately, I don’t have any same-sex spaces or activities. I guess if I was in the bathroom at work it might take a couple of minutes.
I would miss sex so much, but car insurance would go down and a lot of the crime. Eventually everyone would notice though if all the males were snapped out of existence because there just would be as many people.