She can't be terminated because she is sick: doing so is likely a violation of the law (e.g. the Americans with Disabilities Act, or ADA) and she may have a legal claim for compensation. If she is fired because she is sick, she should contact the EEOC to file a complaint.But being sick or even terminal does not mean you cannot be terminated for other, independent reasons. She could be terminated for poor performance, for absenteeism or lateness, for insubordination or violating company policy, or as part of a layoff, restructuring, or reduction in force, etc.