Everything my sister in law ask for my husband gives her - money, dog food, flowers. Over reacting?

My sister in law has no friends and her family mostly is tired of her. My husband gives her everything she wants and asks others to give to her too. Like he suggests they all should do something special for her birthday; but he never does anything for them or for me without doing twice as much for the one sister. After 35 years i am tired of it.