Hudson (Almost Famous) will play Rachel (Lea Michele)'s dance teacher on the musical drama's fourth season.
"[The character is] mean and petty and yet there's a heart there too," Lynch - who plays Sue Sylvester - told E! Online.
"I hear [Kate's] doing just great - I read the scripts and they're hilarious. She gives Rachel a really hard time."
Lynch also revealed that her mean-spirited character Sue will be "momentarily... nice" in the new episodes, following the birth of her daughter.
"I've just given birth to a beautiful baby girl who has Down syndrome and her name is Robin," said the actress. "Which to say hearkens thoughts of spring and new beginnings and her favourite Bee Gee."
Glee will return for its season four premiere - titled 'The New Rachel' - on September 13 on Fox. In the UK, the series airs on Sky1.