。
She reflected on what she had done.
Literal
She [topic-は] herself [subject-が] did fact [object-を] reflected-on.
反省する is a foundational concept in Japanese culture and education — much weightier than English 'reflect.' It means examining one's behavior critically with the intent to do better, and it's drilled into Japanese children from elementary school: end-of-day 反省会 (reflection meetings), 反省文 (written self-criticism essays after misbehavior), and the omnipresent expectation that owning up to a mistake be followed by a public commitment to improve. Without that follow-through, an apology can sound hollow. Translating it as 'reflect on' captures the literal sense but misses the moral weight.