Although Kermit's Mom is seen for the first time in Kermit's Swamp Years, the audience only ever sees her from behind.
She speaks to Kermit one night and gives him advice as he gazes at the stars. Later in the movie, Kermit receives guidance from a star, which, like his mother, is voiced by Cree Summer. This could be interpreted as Kermit having mentally created the star based on his mother.
In his book Before You Leap, Kermit has a section about his mother, stating she had a business career as a talent booker for the area theatre, The Bayou Bijou. Her office was littered with Playbills and flypaper. While working there she discovered acts like Lilly Ponds, The Lipizzaner Horseflies, and Moe Green and His Vegas Cuties. She also booked celebrities like Elton John and Garth Brooks.