We took her out for lunch. When we took her back to the home she asked my sister why I have to come all the time.This hurt my feelings, but I don't put up with my mom trying to manipulate me, but my sister is too soft. She has tantrums when we take her out until she gets her food, too much for one to handle, that's why we go together. She also has multiple myeloma and were afraid she may fall and break something. She's never happy, just wants to come and live with us. She's been mentally abusive our whole lives and we refuse to take her home. I dread going to see her sometimes because of her mood,it's depressing.
If Mom has been abusive, it is kind of you now to try to give her some comfort and pleasure at the end of her life. I hope that your visits are infrequent, since you dread them. You don't have to go all the time. Your sister can visit alone and eat with her at the home or go outside of mealtime, and you can visit alone if that is comfortable.
You are not responsible for your mother's happiness.