What Causes Excessive Fatigue While Treating Syncope?

Hello, I am asking in regards to my mother. My mother is 84 and has been fainting. Not on a regular basis by any means and Now they are telling her she has a condition called syncope. Along with this she has become extremely tired in about the last 4 months. Yes, she is elderly and I understand that you are more tired the older you get but she is tired when she wakes up, all day, and when she goes to bed. She gets at least 12 hours of sleep at night. She has been to the doctor so many times and they continually tell us you have to remember that your mom is getting older Again, I realize that but being as tired as she is I feel there is something else wrong and that she could get some help to help her being so tired all day long. She has no energy to really do anything. We practically have to drag her out of the house to get some fresh air. She is living on the ranch that she and my father worked all their life. She loves the farming/ranching life and was involved everyday working and planning up till she was about 76. I would like to find some answers for her fatigue. I just feel that the medical facility and doctors where she goes is not doing much to help because of her age. I feel she is just a number there. If even that. I keep telling my mother we need to go to Mayo to get some results. Needing some answers. Thank you . A daughter desperate to give my mom some energy.