How to help my Mom stay as oriented as possible?

She lives in her own quarters (small kitchen, bath, front door) on my sister's first floor. I live fifteen minutes away and we speak daily. She can fully care for herself personally but can't remember what day it is or what she is trying to tell me. My mom is 92 and is doing pretty well physically. I just feel her frustration when we talk and she loses her words. What can I do for her?