My mom had a stroke July 2016 and my sister lives with her and is her primary caregiver. Although she is recovering very well physically, she still cannot fully utilize her left hand and she has difficulty remembering to pay attention to her left side. She often times gets angry with my sister and says very hurt full things to her. When I (her other daughter) picks her up to take her to the gym for exercise, she dumps on me with a lot of negative things about my sister. How should I respond?