Quilting is like riding a bike .... once you do it, you can always DO it .... but you don't always WANT to do it .... and certainly not all the time .....
There are a number of reasons people put aside hobbies and passions. Some for health reasons, some for financial reasons, and some for lack of an audience to appreciate his/her efforts, some because they have lost their crafting-quilting buddies.... they develop other interests and just don't have the time to do more at the same time .....you name it ....
Some start too early and burn out ... put it aside for a few years, and start back on smaller projects instead of bed-size, show-quality stuff ...
Maybe she feels your quilting has started to surpass her own mastery and is now overwhelmed or intimidated or feels compelled to push beyond her comfort zone to keep up with the young whipper-snappers that enter quilt shows.
Maybe she's done all the standard, traditional patterns and has run out of ideas....Does she belong to this Board where she can get a spark of new ideas to get her fires rekindled?
Did she do machine and/or hand quilting? .... and now would secretly love to move on to long-arming but feels it is a frivolous expense at this age to invest in the equipment? ...
Is she ready to move on to teaching? ... or giving pep-talks to young quilters? ....
You don't have toalways be "quilting" to be a "QUILTER" ... there are many of us who quilt-a-little but are passionate to see what others accomplish, pay to go to quilt shows to support the art, join in on this board, or just talk it up to the younger generation....
Have you checked to see what your mom's underlying problem is? If it is a "problem" at all ... Maybe she's had an unwelcome change in eyesight, or notices on-coming arthritis, or something else .....
Maybe it's an emotional thing? have all her quilting buddies dwindled by death, retirement/relocation or ill health?
Is she getting rid of the "stuff" by giving it to you - or selling it? .. maybe she has more need of the income than she needs the fabric and all the attendant gadgets? .....
Why does it concern you, personally, that she is giving up quilting? .... These are rhetorical questions... they don't need to be answered on this board publicly. You have to answer only to yourself - I'm not being nosy ... this is between your mom and yourself...... get her to talk it out with you.
You'll find it out .... You are being kind to be concerned ....
I know posts get put on her instantenously and often overlap in content... so if these ideas havealready been said, sorry for the repeat...