He cannot evict his wife through magistrate eviction proceedings. The home may be marital property and subject to equitable distribution if they separate for the purpose of becoming divorced.
This eviction is a ploy to get her out of the house so that he would not have to face a Family COurt judge over this issue.
She needs to stay in the house and contact a lawyer who practices in Family Court immediately. She does have to answer the eviction proceedings and contest them, though. Her answer should say that they are common law married and that the magistrate court lacks "subject matter jurisdiction" to decide this issue. The magistrate will understand that it has to go to Family Court, BUT SHE MUST RESPOND AND CONTEST THE EVICTION.
My comments are not intended to establish an attorney-client relationship, are not confidential, and are not intended to constitute legal advice. Proper legal advice can only be given by an attorney who agrees to represent you, who reviews the facts of your specific case, who does not have a conflict of interest preventing the representation, and who is licensed to practice in the appropriate jurisdiction where the legal issue may be filed or in the state where the law applies.