Negative Personality

I care for a 83 year old lady who still lives alone in her own home.
I stop in everyday to see her and help in anyway that I can. While
I'm there she constantly talks negatively about everyone she knows
that tries to help or just talk to her. I come in with a happy, up beat
feeling and go home just the opposite. It really drains me and I'm
not sure how to handle this. Any input would gladly be appreciated.