First of all...........you should check the markings on the items to see which may be real gold, silver, gold plated, or just fashion jewelry -- and sort and catalog what you have. If you have a friend or family member who is knowledgeable about jewelry, maybe you could enlist their help. It sounds like a big job.
With the possible exception of some real, solid gold/gemstone pieces, the resale value for your MIL's items won't be nearly what she paid QVC. Any "real" items might be taken to a reputable jeweler for appraisal. My first thought is that you or other family members might be invited to select a few items you would enjoy wearing. After that, if you have a good consignment store in your area, you might take some of the items in and see if they're interested in selling them for you on commission perhaps a few at a time.
This is such a sad picture of what happens to compulsive shoppers who get their daily "fix" through TV shopping. Never opened, never worn -- just acquired, hoarded, and forgotten. Such a waste.........