There are a couple of issues involved.
It is possible that the husband sold or otherwise transferred ownership of the copyright to his artwork during his life. If that is the case, then for those works, the widow would not be able to make copies of the artwork. You will have to do some research in the husband's papers to determine if any copyrights were sold/transferred during his life.
If that is not the case, then the next thing to check would be his will. If the husband did have a will, it is possible that he bequeathed the copyrights to persons other than the wife. Again if that is the case, then the wife would not be able to make and sell copies of the the artwork. Or the will could state that the wife gets his copyrights. And of course in that case the wife could make copies of the artwork.
If the husband did not have a will, normally the entirety of the husband's estate
(which would include his ownership of copyrights) would go to the wife. And in that case, the wife would have the legal right to make and sell copies of the artwork (for those that were not sold or transferred during his life).
But whether or not the husband had a will or not, his estate should be probated in order to get a court order stating that any copyrights go to the wife. And once that happens the wife will have complete ability to make and sell the artwork.