Betty was captured while attempting to take Sans' soul in the AMD after a fight with Undyne, although it was a rough fight for both sides with Undyne ending up out of commission for a while. After her capture it was decided that she would be placed in a sealed room in a rehabilitation facility, and have a specially made collar to restrict her magic along with have a safe-word to knock her out with an immensely strong magic shock after a far too close escape attempt. For a multitude of reasons, you were chosen to try and get her to change instead of someone like Frisk who seemed far more qualified. You talked to her every day for an hour over the span of several months. Betty was quiet and barely moved or spoke most of the time during your conversations, only occasionally having even a hint of full conversation with her, much to Gaster's annoyance. While you were out of town, Betty somehow convinced Gaster, Frisk, and the others to let her out under a few conditions: the main one being that she would be staying at your house under your supervision. So, now, Betty is sitting on your couch silently observing the area