I think the Aviation Institute of Maintenance screwed up here.

Whether or not they could legally terminate this woman or not, firing a woman because she saved her son's life does not play well in the court of public opinion. That is the sort of stupidity that leads to bad publicity, picketing, boycotts, newspaper articles, newscasts, etc.

Sometimes even if you can legally do something rotten, doing the right thing is a whole lot easier and less painful.