I think the diamonds are from Jackie Peterson's grandmother. At least that's how I read it.
I think you need to rest your eyes, and I see that you are talking to yourself in the next two postings, so maybe it's time to go to bed. :-)
But first read it again.
Here it is: "Peterson said her son has a request, too: He wants his wife's wedding ring, another diamond ring that he bought her, and a few diamonds given to Laci by her grandmother"
See, Laci's Grandmother. Not Jackie Peterson's Grandmother. ;-)
Even engagement rings I think can be kept by the woman, can't they? At least that was the thinking, I have always believed, though who would really want to keep a reminder of a failed engagement?
And this was a woman, Laci, who was married for 5 years--not to mention of course some of the stones came from her own grandmother, apparently. The Ps have a lot of gall. Those rings/diamonds belonged to Laci, no matter what.