Self-sabotage
The person who claimed to be ill had a perfect reason for cancelling a date. It was evidently good enough that their partner accepted it without any questions. Just when they thought their plan would work, they botched it up by failing to change conversations.
It’s hard to believe that they never noticed they had changed their text with Jenny. They may have been trying to hide something and wanted to get caught.
Breaking point
Infidelity is not a concern for some people. Some people are too busy living their lives to care about hurting anyone else’s feelings. Some cheaters have a strong moral code, even when they’re unfaithful.
Zoe is clearly not happy about having two boyfriends at once. She even says that she’s a bad person for doing so. According to this message she is bound to lose her two boyfriends in the near future.