Margaret was intending to keep Hamish Ascot's surprise proposal to Alice a secret. Though she had to reveal the plans to Alice after the Chataway Sisters spilled the beans about this proposal, Margaret explains that everyone had so much effort in keeping the secret. Margaret then tells Alice that when she meets Hamish during her engagement party, she tells her to accept Hamish's offer, only for a skeptic Alice to reveal she doesn't think she wants to marry him. A surprised Margaret then tells Alice that she mustn't let the chance slip away, since the women of their era are expected to do so, otherwise they end up in a state like Aunt Imogene. She uses her stable marriage with her husband Lowell as an example of an "ideal" outcome for ladies, but she is blissfully unaware of the fact that he is cheating on her with his "old friend", Hattie. When caught by Alice, Lowell tries to blackmail Alice into keeping quiet less she ruin Margaret's marriage, but before Alice can decide she runs off in pursuit of the White Rabbit.
Later open returning to the real world after Alice decides not to marry Hamish, she apologizes to Margaret before explaining to her that she will make decisions for herself as it is her life, which Margaret is surprised by but reluctantly accepts nonetheless. Alice also silently warns Lowell that while she will not tell Margaret of his infidelity, she will be keeping an eye on him.
Margaret is not seen or mentioned in the second film, and it is unknown if she was made aware of Alice and her mother starting their own trading business, and it is additionally unknown if she ever found out about Lowell's cheating.
- Although her married name is never revealed in the movie, the first draft of Linda Woolverton's screenplay called her Margaret Manchester.