I'd guess she moved back to her hometown after finishing studies at Baluart university with rest of the gang, due to lack of money or some similar concerns. She was supposed to get back after she'd find a job at Baluart, but then either cheating happened, or it was already happening before but got serious to the point she decided she'd rather be with her new guy?Am I mistaken or Gillian did not want to live Baluart or something like that?