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She might find one willing to buy them but she won't get much for them, IF they are even willing. Jewelers are not often willing to take a gamble on the history of a preowned diamond, especially when they have no guarantee they can resell it or turn it back into the supply. They usually can get a new stone they know the details of and know they can sell for less than they can pay you. They won't likely take the settings, they'll want the stones, and they won't pay her anywhere near what they're worth. She's better off not selling them at all.
If a jeweler will buy the stones & is willing to buy the gold as well, the most they will pay is scrap price which is next to nothing. Pawn shops will only give you a small fraction of what it's worth. She might be better off selling it herself on Ebay.
Worth is relative. Reality is that she's not gonna get more than scrap, which is literally like a couple hundred dollars. She will spend more on gas trying to get offers than she will get from anyone. It isn't the history, it's that they are preowned. Much like cars, diamonds basically depreciate when you walk out the door. Not really the best explanation but it will give you an idea. They don't hold the value in the secondary market that they did in retail market unless they are somehow provenant, like a celeb owned or bought it or there's a scandal or serious rarity aspect. Appraisals mean nothing in resale, those are for insurance only. She is highly unlikely to get anyone to buy the stones unless they're of some special provenance or the specs and quality are in serious demand and if she gets lucky and finds someone who will, then it will likely be for a pittance because as I said, the jeweler does not know the history of the stones and your word means nothing. They can't resell what they can't prove or trace.
I know it's not what anyone wants to hear, esp in desperate and sad situations but they're worth more in your hands than when you try to sell them.