Answer: avoids any dispute/conflict
Step-by-step explanation:
According to the situation described in the question, Koko's boyfriend likes her a lot but he has some unsure feeling regarding meeting her parents because he is not mentally prepared for it.
Therefore, when Koko asks him to come along to her sister's wedding with her, he lied to her by stating that he already has some committed works to complete as a reason.In this way he trying to keep away any kind of conflict between him and Koko so that his relationship does not has to face any kind of issue.