She's actually not suffering at all. You wouldn't know anything was wrong with her if I didn't tell you.Let her go DL. Make it as comfortable for her as you can but don't prolong her life because the technology and medicines are available.
You have more than enough to deal with as it is. There comes a point where you have to look to what you can realistically manage without doing harm to yourself.
I'll keep her comfortable and add the medicinal mushrooms to her diet as it shouldn't hurt. If she starts to decline, I will let her go. She's had a fabulous life and I know nothing lives forever.