Answer:
Process of elimination
Explanation:
If Olive wants to choose a friend while not playing favorites, while also not being random, she has to eliminate the ones she knows she will NOT take on the trip. She can choose this by selecting the one she knows that will be best on the trip with her, depending on the situation.
Or, if Olive only has one friend, then it wouldn't be surprising that she would take that one friend on the trip, since she has no one else to choose. This way, it is not playing favorites, nor is it random. Hope this helps you!