In this case, I agree with frugal confederate. Your mother gave you that stuff last year--obviously trying to start some kind of family heirloom tradition. It sounds like it would be hurtful and disrespectful of you to sell it…and you won't be getting much out of it anyway. Just keep it, and maybe wear it sometimes (if you like it at all) for holidays or whatever where she will see it. It won't kill you, and it is the nicer and classier thing to do. If you don't have kids to pass it down to, maybe you can sell it in the future when your mother dies. Another thing you could do after she dies is sell it and donate the proceeds to one of her favorite causes.
For the record, I empathize with you big time. I'd rather have the money to invest. And I wasn't comfortable with my mother, and tended to get "bad vibes" from stuff she would give me from time to time. She had good taste, but not always my taste--and I didn't always like her gifts.
Maybe I'm reading too much into it, but there may be an element of control with the jewelry your mother gave you. Like you Will Wear This Stuff because our family needs heirlooms, mementos, items with family meaning…whatever. I know it's aggravating, but I still wouldn't sell it. At least not while she's alive.
