Hi, I'd like to help you with your question.
It sounds like your mother might be a candidate for SAD therapy. Has her doctor talked to her about this type of therapy? It may help her feel better enough that her depression lifts and her anxiety goes down.
She also could benefit from seeing a mental health therapist. Talking out how she feels and getting a better idea of how to handle her depression and anxiety will help her cope better. A therapist could also help coordinate her care and help her if she feels her medications are not working for her. She can find a therapist by asking her doctor for a referral or if she attends church, her pastor may be able to help.
Fear of death is an extremely common fear. It is hard to avoid being fearful since we all must go through it. Fear of death is caused by a fear of loss of control and and fear of the unknown. There are some books that may help her. Staring at the Sun: Overcoming the Terror of Death by Irvin D. Yalom and Be Not Afraid: Overcoming The Fear Of Death by Johann Christoph Arnold. She also needs to speak to either her pastor and/or therapist to help her express her feelings about death.
There are also some books that may help with her depression. One is called Winter Blues, Revised Edition: Everything You Need to Know to Beat Seasonal Affective Disorder by Norman E. Rosenthal. Another is Undoing Depression: What Therapy Doesn't Teach You and Medication Can't Give You by Richard O'Connor. You can find all these books on Amazon.com or your local library may have them available.
Having your support and her family's support is a wonderful way to help your mother. It can make a big difference in how she feels and recovers from her depression and anxiety. To help her, you could try taking her out for just a drive. Getting out of her home, even for a short period, can help her feel reconnected to life. Read to her, bring her dinner, or even taking her to dinner, a short shopping trip, etc can also help.
Keep in mind that caregivers stress can become an issue for you. Be sure you share responsibility for your mom's care and take as many breaks as you can. Treat yourself to a massage, or other activity that helps you renew your energy and feel better. You cannot help her if you are run down and depressed yourself.
I hope this has helped you,