Everybody else got the gist of it.
In addition, each diocese/ archdiocese has its own rules about music in the Mass, and some dioceses are extremely strict about it. I know Rockford is!
I know even 12 years ago in The Archdiocese (there is no other

), my sister wanted “The Theme From Star Wars” played at the funeral Mass of her airman husband, and was told to have it at the funeral home. The flag was removed from his casket at the door between the vestibule and the nave, and the pall was placed for the entire Mass- no national flag, no Cubs hat on top of the casket, and no “Take me Out to the Ballgame”, Star Wars, or “Off We Go Into the Wild Blue Yonder” to close things out. Not even “Theme From Beaches (Wind Beneath my Wings)”. His honor guard was allowed to escort the casket to the back of church, remove the pall carefully as it did the flag, and replace the flag. His best friend was allowed a very few brief remarks after Communion. After the priest finished the Rite of Commital, and only then, was the 21-gun salute, missing man formation, and flag folding allowed. And this is not unsual. I’ve done CACO and funeral duty in the Navy (yes, women can do that), and if the deceased is Catholic, the rites of the Church take precedence over military ceremonies.
This might not solve the situation, but give you another example to use.
When the widow was making her plans with the funeral director and priest, she should have been told to have the song at the funeral home.