If she makes a good faith effort to locate and serve him, and is unable to do so, then she can ask the divorce court to permit substituted service, alternative forms of service such as publication, posting, and mailing to a last known address that are meant to give a person reasonable notice of a legal action if he cannot be located and served in person.

It is possible that a process server in his nation of origin will be able to find him, or that she may be able to get an address from mutual friends or members of his family who remain in contact.