“People don’t know much about me. They buy my Cauldron Cakes — but they never really notice me. I don’t remember the last time someone asked my name”
-- Trolley Witch (CC1.11)
The food trolley lady aboard the Hogwarts Express is a witch who worked on the train, selling treats to passengers and making sure no one escapes. She usually spends the train journeys calmly, going compartment-to-compartment selling sweets, but she can become angry and wield weapons when she has to stop a rider from leaving the train prematurely.
The trolley lady had worked on the Hogwarts Express ever since then-minister for magic Ottaline Gambol personally gave her the job when the Hogwarts Express was created. She was more than 190 years old in September 2016 and could not remember her name for lack of use. She was sharp, though, and recalled the names of students from the past who had tried escaping, specifically Sirius Black and the Weasley twins (CC1.11).
When Albus and Scorpius were escaping from the Hogwarts Express, the trolley lady met them on the roof of the train and told them she had not let anyone escape the train in 190 years and would not let them be the first. She then demonstrated the ability of her pumpkin pasties to transfigure into working grenades, and transfigured her own hands into spikes. Albus and Scorpius got away from her by jumping off the train, and became the first people to escape the Hogwarts Express successfully (CC1.11).