When a person hates his or her sister-in-law, there are two options: either avoid that person or make an effort to get along. Avoidance is not usually feasible, especially if there are family functions both will be attending. The best choice is to practice tolerance and learn how to get along.
The first step towards building a relationship with one's sister-in-law is to be proactive and do what he or she can from their end to improve the relationship. Don't compete with other family members; instead, only concentrate on the sister-in-law. Remain calm and let go of anything that may have happened in the past. Think about and plan for a future of tolerance and acceptance.
Since people tend to respond better to those who are positive, approaching the sister-in-law with a smile and a positive attitude can be beneficial. Think about what is said prior to actually speaking the words. Asking oneself the question, "Is what I am about to say going to encourage her or simply tear her down?" will help filter potentially hurtful words. When it comes to dealing with conflict, one should not attack the sister-in-law. Instead, approach the conflict in an adult manner, avoiding ridicule and not humiliating the other person. Many problems are solved over a cup of coffee and danish rather than with hurtful and attacking words.