IMHO my stash is too big. I would purchase fabric with grand plans to make this or that and then never get around to it. I would find great snags at the thrift stores that I couldn't pass up. Needless to say I have a room to sew in but also have many bins in a small room off the garage. Most of this was from before I started quilting (I used to sew alot of my clothes and clothes for my family).
I have been unemployed now for longer than I would like to admit but we have been able to manage. When we moved my movers asked if I had a bigger sewing room before because there was so much stuff.
I think it is wonderful that you are able to spend time with your elderly friend and help her get better organized. Maybe she has just been overwhelmed by her collection, maybe at her age she has forgotten what she has already bought. Once you get her to a point where she sees what she has the two of you can start a project together to start to whittle away at what she has. Bless you for being there for her.
I don't buy any more fabric "just because" unless it is from the thrift store. I try to stay away from the store and IF I buy it is because it is on sale/50% coupon and needed for a particular project. I have four bankers boxes, plus two baskets and a sewing suitcase full of paper patterns that I have plans to put on the web.
But having this stash also gives me resources to be creative. I made all four of my grandkids (9, 6, 5 & 2) flannel lined jackets for Christmas and only had to by the lining (that was on sale) :-) and four of my WIPs came directly from my stash.