Please don't think for once that you are the only one in your situation, God bless you for caring for your mother now in her situation. I know first hand how hard it it to care for a sick person, for I am taking care of a terminally ill daughter. I have heard they all resent their caregivers, and get very angry, and depressed for being so sick. They only see their situation, and can't stand to see others in better health than they are now, specially if they have been very independent for many years. I'm sure she still loves you very much, and appreciates what you are doing for her. Sometimes if they are on medication the side affects of the medication makes them that way.
Lord help this child of yours with her/his mother, give her/him the wisdom they need to keep helping her/his mother. Father in heaven give her/him the strength needed at this time to keep on helping the mother. Bring their bonds stronger than ever, and have the mother show some appreciation of what her child is doing for her. Bless them both I pray in Jesus mighty name, amen. May the grace of God be with you both.
Isaiah 40:31
Yet those who wait for the LORD Will gain new strength; They will mount up with wings like eagles, They will run and not get tired, They will walk and not become weary.