Your adult sister can be your best friend, your worst enemy or somewhere in between. But even if you and your sister have a good relationship, the same habits that irritated you when you were younger can still get on your nerves. Learning to deal with an irritating adult sister in new ways can help both of you enjoy each other more.

Reverse the Rivalry

Adult sisters who revert to old sibling rivalries may irritate each other more than those who leave the past in the past. Whether you are 20 or 50, bringing up the time she told your mom about something you did in the heat of a conflict just makes things worse. Work on bringing your relationship into the present by agreeing not to use past hurts against each other. The more you practice appreciating and acknowledging your present relationship with your sister, the less small things will irritate you. According to Jane Mersky Leder in Psychology Today, sibling relationships are not static but change dramatically over time. Understand that how you communicated as children should not dictate how you communicate as adults. Your current relationship and your life's experiences should inform your communication rather than old sibling rivalries.

Adult Conversation

Resist the temptation to fall back on old communication styles with your sister to help you deal with her irritating ways. Not responding to emails or texts, missing family events and talking to everyone else but her will only add fuel to the fire. Set personal boundaries about the things you will and will not talk about to help you stay in control of your emotions. Turn conversations around to topics that better reflect who you are now to make your sister aware of where you will and will not engage. Brigham Young University's Forever Families website reminds adult siblings that some basic communication principles, such as avoiding sarcasm, being a good listener and paying attention to verbal and non-verbal behavior, can help you understand your sister better.

Learn to Laugh

When your sister irritates you, laughing together helps diffuse the situation. Shared memories, dating disasters, bad haircuts or embarrassing moments can remind you and your sister just how much you have been through together. Advocates for Youth reminds families that laughter can be a great escape valve for family tension and can help you see yourself and your sister in an objective and honest way. Focusing on the fun and the funny rather than on the irritation helps you remember why you love each other.

Share Your Feelings

Part of being an adult means knowing when to share your feelings. Your sister may or may not be a person who can understand your feelings, validate them and apologize for irritating you, but talking about how she makes you feel can help you let go of the anger. The article "10 Ways Siblings Can Drive You Crazy" on the CNN Living website recommends being assertive but not aggressive. Keep the focus on changing your responses to her rather than changing her behavior while letting her know how her behavior makes you feel.