How to answer
On my soccer team in college there were two girls who did not get along. Even though our team was really good overall, having two girls talking about each other behind their backs caused drama and made it uncomfortable for everyone else on the team. I spoke with each of them separately to try to understand what the problem was. When I found out it was a misunderstanding, I encouraged them to try to work things out, letting them know it was negatively affecting the rest of the team. Since the greater goal was to have fun and win, they agreed that they would be willing to make peace.
It's not necessary to go into great detail about the situation, but share enough to give the interviewer insight into your experience handling and resolving conflict, enough info to instill confidence that you can deal with these types of situations.
"When working with people, it is only natural that this occur once in awhile. My role is to build bridges in relationships. I preach conflict resolution based on humility and the intent to resolve problems while strengthening relationships. I encourage individuals to take pride in being accountable for their own relationships and therefore, work things out by approaching another in private to discuss the issues at hand. If necessary, I will intervene to mediate a discussion."