"Amy, this is Taylor's other mom, Cheryl."
Susan was a single-shot character from the penultimate episode, "Down a Tree." Susan is a noteworthy character, because she is most likely the first gay/lesbian character in a Disney Channel series. This may not be the only time that Disney does something similar to this. Her partner, Cheryl, also appeared in the episode, and it also turns out that they're the proud parents of a young girl named Taylor, who is also Charlie's playmate for today.
She was only seen in the episode "Down a Tree," the penultimate episode before the series finale "Goodbye Charlie." She was the mother of Taylor, Charlie's playmate, and she also introduced her partner Cheryl to Amy and the other Duncans. Naturally, Bob was feeling awkward around the couple, since it was different to what he was used to, but he never questioned the couple as being different from a regular couple. In fact, Susan got into a fight with Cheryl over who they were hanging out with, much like how an ordinary couple would often bicker. At the end of the episode, Susan leaves the Duncan residence with her wife and daughter, and Amy tells Bob that no matter what kind of couple they would ever come across, no one would ever think that his bug jokes would ever be funny.
Susan was a rather serious woman, unlike her wife Cheryl who had a slightly bubbly attitude.
She wears a red blouse, and has medium length, blond hair.