They never legally were married only by common law. When does a common law marriage say that she is entitled ? they have been together off more than they have been on.
It really depends on whether they have a valid common law marriage. If the common law marriage is not valid then such is a defense to teh divorce complaint. If a valid common law marriage does exist then a divorce is necessary to terminate the union. A valid common law marriage will create the same rights as a formal marriage.