Mrs. Sanderson is the wife of Mr. Sanderson. She hates the fact that her husband bought Chibi-Robo even though they barely had any money, but still respects Chibi and likes what he does in the house. She eventually starts liking Chibi even more as the game advances and starts calling him "Cheebo". After Chibi Robo finds the toy reciept, Mrs. Sanderson locks herself in the bedroom and critizies her family's habits, threatening divorce.
Mrs. Sanderson tries to be the voice of reason and down-to-earth about things. She worries about the mounting bills from Mr. Sanderson's needless spending of Moolah on Drake Redcrest collectables, and gets pretty sarcastic about his hobbies, even wanting to sell all of his Drake Redcrest collectables in a garage sale! She also worries that Jenny will never take that frog costume off, and be rid of it. On the other hand, Mrs. Sanderson does admire Jenny's skill in art, and wishes that she herself was able to draw.
However, in Giga-Robo's recorded memory and when Chibi-Robo and Telly go back in time 10 years in the Alien's transport shuttle, it is revealed that Mrs. Sanderson was almost like Mr. Sanderson in behavior, and was enjoying the fun that he, herself, and Giga-Robo were having together before the burden of the financial difficulties set in.
Mrs. Sanderson's attitude to Chibi-Robo ("Cheebo") is as if it were a an actual person, despite it being the size of a very small action figure. She sometimes makes positive comparisons to it and complimenting it for its duties, as opposed to her husband and daughter. In the plot where she locks herself in her room after telling off her family, Mrs. Sanderson confesses that after her own boycott against work in retaliation that she never knew how boring it is to not have anything to do.
Later in the story, when Chibi-Robo opens the suitcase with Giga-Robo's Leg, the larger Spydors start attacking Mrs. Sanderson, prompting her husband to break down the door and rescue her.