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She wrote about gender bias in science.
Literal
She [topic-は] science [in-における] gender bias [about-について] wrote.
~における is a formal compound particle attaching に + おける (the attributive form of the literary verb をる/居る), used to mean 'in / at / concerning' a domain or context. It's the academic-prose cousin of で and 中で, and you'll meet it constantly in essays, reports, and theses: 日本における若者の意識 ('young people's attitudes in Japan'). Pair it with ~について ('about'), and the sentence has the clean register of academic or journalistic writing. 性的偏見 in this context most naturally reads as 'gender bias' rather than literal 'sexual bias' — 性的 covers both senses, and academic discussions of 'bias against women in science' are exactly the kind of context where this phrase appears.