When I said (above) “at least 6 months”, I was not saying that on the basis of halacha (which others have already addressed), but on the basis of the emotional/psychological baggage that the person is carrying.
I think a person who has been (obviously UNhappily) married for a period of time needs a while to re-adjust to seeing themselves as a seperate individual before becoming, again, “basar echad” with someone else.