This witch, also called wicked witch, is a minor character who appears in Shrek and Shrek the Musical.
She was seen as a fairy tale creature banished to Shrek’s swamp. Later, she sings "Freak Flag" with the other creatures.
In the first Shrek film, during the scene where the Duloc guards are rounding up the fairy tale creatures, there is a witch present. Upon being rounded up, her broom is snapped by the guards.