Shelley, what a special daughter you are! There are so many wonderful ways to say thank you at Disney and your mom is very lucky!
You might want to consider a fireworks cruise for your mom and they depart from the Magic Kingdom resort marinas as well as the EPCOT resorts for Illuminations. The costs for these range from around $225-300. It is pricey but a wonderful experience. Another idea is to sign her up for a tour. There is quite a variety of different interests, duration, and cost. Check out both the cruise and the tour options on the disney website,
www.disneyworld.com, under Discover then Tours and Special Experiences.
The one thought that comes to mind when thinking of a special gift to commemorate her stay is something from the Arribas Bros either in Downtown Disney or on Main Street of the Magic Kingdom. You can select a perfect mug or glass or vase etc and then get the piece engraved with your mom's name and date perhaps. Sometimes they can do this while you wait but my suggestion would be to stop there early in your day at the park. Ask about resort delivery as well.
Don't forget about the wonderful disney florist! (
www.disneyflorist.com) They have all kinds of items and arrangements to choose from in a wide range of prices that can be delivered to her room. Check out their website to see some of the choices available and if you don't see anything that quite fits your needs please don't hesitate to call them directly. 407-827-3505 The cast members love to help you make special and personal gifts.
Again, have a fabulous trip and take many pictures to commemorate your vacation!