Winifred is shown to be a member of the suffragette movement. But by the time of the film, she has become so consumed by her meetings and protests that she neglects her children. However, she is shown to be slightly more caring and attentive to them than George. She is also depicted as being devoted to him, but like the children, he unintentionally neglects her (and is somewhat abusive to her). She has blonde hair and is usually seen wearing traditional attire for women in the Edwardian era of the 1910s.
Originally, her name was going to be "Cynthia", but this was quickly changed to the more "English-sounding" Winifred after some issues with the script; however, some alternate universe fan fiction stories have her name written as Cynthia. Though she and Mary Poppins are never depicted speaking to each other in the film, the former does mention the latter frequently. In the book, they do so.
It is revealed that, prior to the events of the film, Winifred had been in charge of hiring nannies to care for Jane and Michael. Unfortunately, they had all been, in the words of George, "unqualified disasters". Thus, she is pleased when he decides to select the next nanny himself. Also, she is responsible for organizing the house staff to respond to the cannon firing of Admiral Boom at 6 pm and 8 am. She and the household staff go around and secure the breakable objects, which will rattle due to the cannon firing. Her theme throughout the film is "Sister Suffragette", which serves as her introductory song; the melody also serves as her leitmotif.
Winifred first appears at the beginning of the film. After singing about the suffragette movement which she is a part of, Katie Nanna, the current nanny, informs her that Jane and Michael have run away. She is annoyed, as it is the fourth time that week that they had gone missing. She then reveals that she has chosen to quit, due to their horrible behavior. This shocks Winifred, and she makes an impassioned but failed, attempt at convincing her to stay.
When George comes in, it takes Winifred several tries to get him to realize that the children are missing. He chooses to deal with the matter immediately, by calling the police. Just as he gets on the phone, Constable Jones comes by with Jane and Michael in tow. He reveals that they had not run away intentionally, but had gotten separated while dealing with their kite, which had gotten out of control and broken. Winifred goes to embrace them, but she is scolded by George for getting emotional.
After the children are sent upstairs to the nursery, Winifred and George discuss the matter of hiring a new nanny. Noting that the last six, hired by her, had all been failures, he decides to hire the new one himself. As he dictates, she writes up an advertisement for a strict one. When Jane and Michael come with their own ad for a kinder one, she is the one who encourages George to listen. She is charmed, but he dismisses it as ridiculous.
The next time Winifred is seen is after George has "hired" Mary Poppins. She briefly comments on her to him, though he is still confused about the matter. The day after, she is seen at breakfast, talking with George about how cheerful the household has been since Mary was hired. Her observations are confirmed, as Jane and Michael come in, both very happy, and bring her a small bouquet of flowers. However, George is not so cheerful, which she interprets as him being out of sorts, which infuriates him. However, he tries to defend himself by saying that he has no objections to being cheerful or pleasant, he does expect "a certain decorum" in doing so.
That night, at George's demand, Winifred observes him attempting to fire Mary, due to the outlandish stories from Jane and Michael. However, instead of being fired, she is able to trick him into taking Jane and Michael to the bank where he works.
The next afternoon, Winifred is shown in a panic, as she is late for her meeting. When the doorbell rings, she is shocked to see the children, whom she had expected to be with George. Bert, who had taken them home, explains that they had been frightened at the bank by George, and needed someone to look after them. She immediately thinks of Mary but is crestfallen when she realizes that it is her day off. Since neither the cook, Mrs. Brill, or the maid, Ellen, can look after them, she hires Bert on the spot before quickly rushing off to her meeting, leaving him a bit confused. She returns home afterward to find a swarm of chimney sweeps partying in the house. Several of them notice her suffragette sash and begin marching with her.
Winifred is next seen in the morning, worried to death about George. It is revealed that he had not returned home after being fired from his job, so they have called Constable Jones to report him missing. She scolds Ellen when the latter suggests that he may have gone to a bridge "popular with jumpers". Along with the rest of the household staff, she is relieved when he comes and reveals himself to have been in the basement. Having had a change of heart after his firing, he had been working on mending Jane and Michael's broken kite. She chooses to contribute as well, utilizing one of her suffragette sashes as a tail for it. She is later seen listening, as Mr. Dawes Jr., one of George's old bosses, talks to him. The bank owner, Mr. Dawes Sr., had died the night before, but thanks to a joke told by George, he had died happier than ever in his life. Out of gratitude, Mr. Dawes Jr. offers him a partnership in the bank, to which Winifred reacts by happily kissing him. She is last seen looking on happily as her children fly their kite.
Winifred does not appear in the sequel, which takes place twenty-five years after the original film, but she is briefly mentioned by Jane as Micheal nearly threw away the kite as Jane says "Remember that kite, we used to love flying that kite with mother and father". There are also photos of Winifred and George all around the Banks' house.
One of her Suffragette sashes is seen on the kite (like the first film). Additionally, Jane has grown up to have a similar personality like the one of her mother, giving away pamphlets for the workers' syndicate movement to which she works.
The character of Winifred appears in the musical. Some details of her life are changed. Instead of being a suffragette, she is a former stage actress who is struggling to enter George's social circle. She is aware that she is failing her family, as shown in the song, "Being Mrs. Banks", but George is confused as to why she finds marriage and motherhood so difficult. In an attempt to please him, she organizes a small tea party, but it fails as none of the invitees appear.
In Act II, after Mary leaves, Winifred hires George's harsh former nanny, Mrs. Andrews, in an attempt to please him. Soon, the Banks become shocked at her tyrannical behavior. Later on, encouraged by the children, she goes to the bank to be at his side as he faces the chairman. She arrives intent on defending him but discovers that he has become the hero of the hour. He apologizes for underestimating her, and they return home. As Mary leaves, they waltz happily together.
- Winifred is briefly mentioned in Saving Mr. Banks when the Sherman Brothers perform "Let's Go Fly a Kite" as they say, "and Mrs. Banks runs threw her house and takes the suffragette ribbon and says "A kite needs a proper tail, don't you think."
- While Winifred nor George don't make any appearances in the Disney parks, women dressed up in suffragette outfits can be found in Main Street, U.S.A. at the Magic Kingdom, and "Sister Suffragette" can now be seen being performed there, too.