Catholic Girls Do Not Get Divorced!

Catholic girls do not get divorced or so they say. So what happens when a Catholic girl’s husband philanders and files for divorce? Where does that leave her? She hasn’t sinned as long as she was faithful to her vows but she is damned by the Church unless she obtains an annulment. Please tell me how a marriage of 25 years and four children could or should be annulled? What is it that I am missing?