First stages of Dementia

My mom just started maybe six months ago with symptoms. We finally got her to go to the neurologist and she started to take aricept but had to cut the starting does in half due to nighmares and feeling sick. What could she take to aid with the aricept . Her symptoms is short term memory mostly. She is also taking thyroid med's low thyroid which they said could be the issue but her mri showed aging of the brain. Her mom died of dementia and it was so hard to watch happen. She doesn't want this to happen to her. She is scared, depressed at times. She lives alone and I try to be there for her for the important things. I live 1 hour away and have three kids I homeschool. She functions fine , but when she gets nervous or flustered she forgets things. They did the dementia tests on her and she got so nervous she couldn't make a clock for them right. She forgot how long she lived places and got info all mixed up.
HElP please. I hate to see her this way. One minute she seems fine the next.... not so much. Thank you.