Can Sudden Hearing Loss Be Reversed?

My 17-year-old daughter was seen in the ER for loud buzzing in her ear. She thought a bug had gotten in her ear, but it turns out it was an episode of sudden hearing loss. It is a mixed hearing loss that includes both sensorineural (inner ear) and conductive (stapes) components. Is this a medical emergency? Do I need to get her to an ENT right away? I ve heard that sometimes nerve damage from sudden hearing loss can be improved or corrected if treated within 2 weeks.