Hi, Theatrechick!
I know where you are coming from too!
I hoard and I love it! Sssshhhh. But I have finally decided to purge AND get organized. So I just plan on taming my stuff.
If you are committed, you will do it. Don't even worry about it. Just "Keep on Truckin' ".
As for your Mom, get her to sit down and watch "Hoarders". It worked for me and it might let her see that there are other people with similar and worse problems. There are not TOO many people worse than that lady with the expired food, for example. She has to be on the very extreme end.
That might help and it is worth trying. When I get in a lull, I watch it some more. Your Mom is likely viewing her stuff in a similar manner. If and when she is in the mood- just help her out. Let her know that eventually a little work every day will go a long way.
Also, take photos of beloved junk! I had an old suitcase that had travelled with me all over Mexico. I spent years living out of that "buddy". It developed a little rust inside, it is rather large and I wanted to get rid of it and I did not. I could no longer use it. I finally just took a photo. That made tossing it much easier.
I, for one, am a perfectionist. I have to do things near perfectly or I do not want to do them at all. While teaching I was extremely organized (at work). I have filed for years and that sure helped. But I am going to try to transfer those skills which I already have to my home.
You might want to think in terms of the size of things too. I learned that from travelling. To keep birthday cards etc. for me is not a problem. All of them, decades worth, have fit nicely into two file boxes. I did get rid of the envelopes which certainly helped.
Recently I merely threw out a few turtlenecks that had shrunk and suddenly I could move my hangers in the closet! Liberating feeling.
You might enjoy the forum on "Addicted to Decluttering" or something similar. It can be fun.
As for the craft supplies- been there, done that. If you want to keep some, do it for yourself. I recently bought a 7 drawer Sterlite rolling plastic organizer and it is terrific. It was under $35 and I read about it on this website. Now I can eat on my kitchen table! I'd like to get about 6 of them! LOL. But I do not need quite that many.
Also you can sell what you do not want on Ebay. I do it. :o)
Good luck! I love the idea of creating something with/about your cool stuff!