1) As a general matter, it will depend on what forms or documents she signed as part of receiving the settlement. Except as set forth below, if she signed anything (as is likely) stating that the $500 was payment in full of all claims or giving up her right to sue, she can be held to that and would have given up he right to sue or seek further compensation.2) If she did sign something like the above, IF she could be shown to have not been mentally compentent (e.g. due to PTSD or depression) at the time she signed it, it may be possible to escape the terms of the settlement: only mentally competent people can enter into contracts, including settlements. This would be a difficult thing to show: the presumption is of mental competence, and it would require compelling medical evidence or testimony of incompetence to escape any such settlement agreement.