A good education taught her how to teach. She has a 4 year degree, then some sort of 1-2 year program of being essentially an apprentice, and then you must take several college classes every few years to demonstrate your continued learning, and oddly IMO, the same school that was adopting weird and unproven teaching methods around reading was giving their teachers fairly good yearly workshops about how to teach.
She has a genuine-ness that is palpable, something that I've also inherited. My girlfriend describes it as "You have golden retriever energy" and it gets people engaged with you. She's a very fun teacher.
She treats kids like people, yet the way the interactions go and the way she gets to kids ensures that they still generally respect her. She also used to have an administration that recognized her talent and value, and would stand behind her when a kid was a serious problem. She has helped "bad" kids do better, and helped bullied kids, and has helped needy kids, and this gives her a sort of legendary status. Everyone knows and loves Madame.
She was well experienced dealing with stupid shitheads because she grew up next to my dad's family (lol small towns) and raised three kids that were pains in her ass in diverse ways.
She works her absolute ass off. She habitually showed up to work ten minutes late (ADHD runs in our family quite bad), but the admin ignores that when she is teaching every student in the school and grading assignments until 8pm most nights, and building the curriculum for all the other teachers. I once stayed up with her until early in the morning grading a writing project she had given. Hundreds of students, every year, and she would always know their name and lives and all about them even though she's bad at remembering names otherwise. She was willing to teach kids how grammar worked and how to diagram sentences when they came into her class and didn't know. She was also able because of her education.
She comes from a family tradition that treated education as a total good, something everyone should seek out as much as possible, and something that would lift you up, along with your family, despite ostensibly being a very rural lineage. We have the journal of a woman in our ancestry 200 years back talking about how she learned to read and write because that's just how great education was in general. We aren't nobility or anything that would traditionally do that kind of thing.
A crazy mix of genetics: We are all super neurodivergent and probably super inbred and the latest generation is experiencing crazy illnesses and autoimmune disorders, but my mom's family consistently scores above average on standardized tests and has done so for generations. So she has a good brain to use the things she learned, even though there's tons of "smart" things that isn't so good at. The role of a good educator just happened to really fit well with her mix of beneficial and problematic brain issues.
So, you know, luck. She picked this career path because she was 20 and her marriage failed and she suddenly had to support three kids. Turns out she's really good at it. We aren't ambitious people, but this general theme is the same for my entire extended family.