I feel bitter towards my little sister all the time
Why would you feel bitter towards her?
I think she is an ungrateful little brat who is used to getting everything she wants.
Sometimes kids can be bratty but if you're the older one then you should keep your cool. She will eventually grow out of it.
I've been good to her but she calls my name for hours. Like she doesn't fucking realize
I understand your anger, but you need to learn to let the small stuff slide in this situation.