Who is it? Laura Bow? I have heard someone say it was Roberta, but it looks a lot older than the person you see when you die (who is clearly Roberta).

Are you referring to the painting of the woman in the parlor of the old mansion? Probably not. Sierra loved putting easter eggs and cross-promotional tie-ins in all their games, but didn't bother putting them in without making the reference blatantly obvious. There's no detail revealed about the subject of the painting when you LOOK at it, so it's likely just a painting of random mysterious woman.

I think never knowing the subject of this painting, as well as the subjects of the two in the entry hall, was intentional, and makes the mansion all the eerier and more mysterious.