Your relationship with your siblings will last longer than any other relationship -- if you can manage to get along. Family dynamics are sometimes difficult to navigate, and it's especially true with siblings. No one can push your buttons quite like your brother or sister. A sister who tends to be annoying may be difficult to deal with, and if you tell her to simply calm down, it might set her off even more. Instead, use other tactics to bring order to the situation.
Control Your Response
Remain calm. Try not to react in like manner to your sister's hysterics. Doing so gives her control over you and gives her a response that keeps her going. Instead, remain in control of your emotions without stooping to her level. Try to act opposite of her behaviors. If she shouts, talk in a quiet, calm voice, for example.
Practice Active Listening
Listen to what she is saying. Allowing her to talk without interrupting or trying to immediately solve the problem validates her feelings and may help her calm down. This allows you to have a productive conversation that can help ease the situation. Reply calmly. A soft, soothing tone will go a long way toward calming her down.
Throw Her Off With Your Response
Disarm her by giving her a response she doesn't expect. If she is annoying you in a childish way, such as putting you down, for example, a lighthearted joke may be enough to shock her out of it. Or, do something unexpected by giving her a compliment. This only works, however, if she is upset over a serious issue. Be careful that she doesn't think you are making light of her situation.
Move to a Different Location
Move to another location. Chaos breeds chaos. If she is hysterical and is in a location where there is a lot of noise or distractions, move with her to a quiet, soothing space. Sometimes the change of location can be just what you need to work through the problem.
Ask other family members to help. A sibling can be your worst friend or your best enemy, and if your sister is looking at you like she would an enemy, it might be best to bring in reinforcements. Some fatherly advice, for example, might go a long way toward calming her down, or just a warm hug and some gentle understanding from her grandmother.
Don't be a doormat. You may love your sister, but you don't have to take abuse. If she is verbally abusive, remove yourself from the situation. Tell her that until she can treat you in a respectful manner, you will not have anything to do with her.