"Holy mother" is a powerful phrase that is often used to express astonishment, wonder, or surprise. If you are looking for alternative expressions to substitute for "holy mother," you can consider using other religious references such as "divine parent," "sacred nurturer," or "heavenly guardian." Other options could include "miracle worker," "supernatural force," or "mystical presence." If you want to keep the religious connotations of the phrase while still varying your language, you could use "blessed mother," "saintly matriarch," or "godly matron." Ultimately, the choice of the synonym depends on the context and the degree of emphasis you want to convey.