Letting players connect with their friends is a great engagement tool for your game! PlayFab offers you the ability to integrate with your players' existing social network (like Facebook, Steam, or Xbox Live) or to manage your own custom friends lists within your game.
Any player in your title may be friends with any other player in your title. Notably, friendship on PlayFab is a one-way street.
If Julie adds Bob as a friend, there is no approval process for Bob. In fact, Bob may be unaware.
Bob must separately add Julie for the friendship to be mutual.
If you wish to have reciprocity rules, it is your title's responsibility to enforce these conditions with a custom game server or CloudScript logic, if necessary.