Be thankful. As odd as it might sound, I'm quite serious.
Your mother, as difficult as it might be for her to speak about, and you to listen to, is saving you a huge amount of headache in the short and long-run.
I can't even get my parents to have any serious conversations about anything like this, and as they get older, I start to wonder what will or won't happen when the time comes. My mother isn't in much better health than yours, and she categorically will not discuss anything, nor will my father, and neither of them will put anything in writing, so between the two of them, whichever one goes first is leaving the other with a nightmare, and when they're both gone, I'll be in a real bind.
These conversations are difficult and can be contentious, but they need to happen.
I offer these suggestions.
1. As Andy said, get everything written down as to her wishes.
2. Determine if pre-need arrangements have been made.
3. Have a medical proxy, homestead declaration and living will ready to go. Most lawyers will do these for free or very, very inexpensively (generally no more than about $15-20 in this area.)
4. If the probate courts in Alabama are as much of a mess as they are here, make absolutely certain a will is present, or you could end up losing anything of value, including family heirlooms, photos, cash/stock/commodity accounts, and any real estate. A simple will is usually $100-200, plus probate filing fees, which vary from state to state. But it's money very well spent.
5. Make sure you know where all the accounts, holdings, etc. are.
Beyond that, it's okay to be scared for yourself, her, or both of you. It's human nature to be concerned. But, don't let that worry monopolize your mind or take away from whatever time might be left. Enjoy it as much as possible. She'll be more at peace, and so will you.
Hang in there. We're all behind you.