Final answer:
The change in Farah and Rebecca's relationship is most likely due to the transformation from a dyad to a triad, altering the group dynamics and potentially affecting their interactions.
Step-by-step explanation:
In the scenario described, the change in Farah and Rebecca's relationship is most likely because of the transformation of their group from a dyad to a triad. A dyad consists of two people whose relationship ceases to exist if one person withdraws. In contrast, a triad introduces a third member, which creates a different dynamic, potentially leading to two-against-one situations or a changing majority opinion. Georg Simmel wrote extensively on this subject, noting the significant shift in group dynamics that occurs when transitioning from a dyad to a triad. This change can influence how relationships are experienced and maintained, as individuals navigate the complexities of a three-member group.