I am sure your mom and sister feel terrible already. Sometimes it is hard to know what treatment is best for our chickens and sometimes there is nothing we can do to help them. It is very hard to lose a beloved pet.
I wasted many years hating my mom, I even moved across the country so I would not have to be around her. As I got older I spent more time repairing our relationship and forgiving her. She died last summer and I am so glad she knew I loved her no matter what happened in our past.

Try not to hate anyone, as they were only trying to help no matter what the outcome was.