Answer:
Social Facilitation
Explanation:
Social facilitation refers to a situation when a person perform better in doing a certain job/task when other people are around to witness the performance.
Typically, this can be explained by people's desire to maintain positive social status. When other people see your performance you tend to put more effort in order to impress other people in your social group.
In the example above, We know that Samantha has an easier in controlling her diet when she's alone.
But when she's eating with her friends, she experience a certain form of social pressure that make her want to maintain a certain social status. If for example, all her friends are eating a certain type of foods or drinks, she might feel afraid that her friends will consider her to be rude or weird if she's not doing the same.
