Which agency emailed you on October 27, 2021, USCIS NVC or the U.S. Consulate General Cuidad Juarez, Mexico? If it was not from Cuidad Juarez, you will have to await their email notifiction that your Mother is eligable to schedule an appointment for her interview. Likewise, you are always free to call the Cuidad Juarez Consulate Immigration Visa Section for further clarification or assistance asking what the projected current wait times are for their notifying you of your Mother's eligiablity to schedule an interview appointment. Buen suerte!