Maria Maria Minchin is the headmistress of Miss Minchin's Select Seminary for Young Ladies in London, the boarding school where Sara Crewe is enrolled. She is a dominant, unfriendly, and often cruel woman whose primary concern is the reputation and financial stability of her school. She welcomes wealthy students with a display of warmth but treats those without money with coldness and contempt.

Her motivations are rooted in her deep obsession with the seminary, which she built through years of hard work after a poor upbringing. This background fuels her resentment toward those who appear to have advantages she lacked. When a misunderstanding shortly after Sara's arrival leads to Miss Minchin being humiliated in front of the class, she develops a lasting grudge against Sara, viewing the girl as rebellious despite continuing to use her as a show pupil to attract other wealthy families.

The turning point in their relationship comes when Miss Minchin learns of the diamond mines Captain Crewe has invested in. Believing Sara's family will become even richer, she spends a considerable sum arranging an extravagant birthday party. When news arrives that Sara's father has died and the investment has failed, leaving Sara penniless, Miss Minchin feels deceived and personally wronged. She forces Sara to become an unpaid servant in the school, treating her even more harshly than the other maid, Becky. Her cruelty toward Sara is driven by a combination of financial loss, wounded pride, and the lingering resentment from the early humiliation.

Miss Minchin has a younger sister, Amelia, who works alongside her at the seminary. Amelia is noticeably kinder and occasionally tries to temper her sister's harshness, though she lacks the courage to stand up to Maria directly. Miss Minchin also maintains a complex relationship with the student Lavinia Herbert, who sees through the headmistress's manipulative nature and shares her jealousy of Sara.

Later episodes of the series reveal more of Miss Minchin's past, showing how her difficult upbringing and relentless effort to build her school shaped her obsessive and controlling personality. She is not presented as a purely one-dimensional villain, but rather as a character whose harshness stems from insecurity, pride, and a desperate need to maintain control over her institution. Her notable ability lies in her shrewd understanding of social status and finances, which she uses to manage the school and manipulate those around her. Physically, she is depicted with gray hair worn up, green eyes, and glasses, typically dressed in formal Victorian attire. Throughout the story, she remains the primary source of conflict for Sara, consistently working to undermine her spirit while Sara's resilience and kindness ultimately prevail.