Such a personal question. I was helped somewhat in this answer by a book about widows put out, I believe, by TIAA-CREF. They interviewed hundreds of women who had been widowed. On the chapter of beginning again, there were those who said that they were approached by men too soon, and when they were more ready for a relationship, then, the men were no where to be found. And they were very lonely.
I would have to say that only the person involved knows the answer to this question. And at the same time, even if a widow does begin to have another relationship, that in no way diminishes what she feels about her late husband. Those feelings never go away, even though the widow might begin “living” again.
If you are asking this for someone else, don’t expect to be able to rush her.