To sell effectively, what you need is a detailed inventory of all those treasures that are wrapped in boxes, including the type of pieces, dimensions, marks on the back with pattern name and maker's name and, very important, the precise condition. Condition makes a HUGE difference in what price an item might realize.
I will alert some collectors in your area that you wish to sell. Perhaps one of them or someone looking at this site will contact you. There are also businesses that will sell things on eBay for you for a percentage of the sale. Google can help you find one. There are also reputable auction houses who would help you dispose of the collection. Then there is the FBICC. Besides this free message board, if you became a member you would have access to all the selling venues in the Club, including the convention auction, regional meeting table sales and the For Sale section of the Club's newsletter BlueBerry Notes.
Here's hoping you'll find the best selling avenue for your mother's lovely collection.