The first thing I'd do would be to get her husband's death certificate. This will probably tell you whether he was a widower or not. This will at least narrow the search. If Harry left a will (not only the rich did that!) you might also get some clues.
It's also possible that Rosina remarried - try looking in the marriage indexes for the years after Harry's death.
Also, telephone directories for the period may list Rosina.
Good luck
Lesley
