My friend is having tonsillitis in work but is tonsillitis contagious through talking?

Maybe: Tonsillitis may be caused by group A strep, strep pyogenes, and therefore may be considered contagious however just talking will probably not spread it by the respiratory route. Wash hands, avoid close contact, kissing, and sharing beverages, shaking hands then touching the face. In other words take precautions. After 24 h of antibiotics no longer contagious. Viruses, fungi also cause tonsillitis.

Not likely: Talking no, kissing, sharing eating utensils and cups and not washing hands well, or others not covering their coughs are much greater risks for spreading tonsillitis germs.