No matter what I do, my mom will almost always find something wrong with it

It is very difficult to move from being the child to be the care giver as in your situation. Your mother's behavior as you describe it is a part of this disease. As the disease progresses and she is less aware of the present including her surroundings and who she is speaking to. Your response of anger and frustration are understandable. It is also a part of the grief process as you see you mother slipping away mentally. In the moment that you feel the anger step away, take some deep breathes and give yourself time to calm down. Then return to whatever you were doing with her. Caregivers of Alzheimer's patients need a lot of support themselves. There are support groups  as well as respite services available in many areas that will help you understand the process that each of you is going through. You can get more information about Alzheimer's disease and local resources by going to www.alz.org