It's unfair that one person gets to have more freedom than the other and in this case, the sister gets to stay out later even though the curfew for both should be the same
Consider the statement "My sister gets to stay out as late as she wants but I have to be in at 8 PM". Is the statement "I hate that my sister gets to stay out as late as she wants while I have to be in at 8 PM" false? Yes/no/unknown