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She made her dream of becoming a great scientist come true.
Literal
She [topic-は] great-scientist [to-に] become [called-という] dream [object-を] realized.
The frame [clause]+という+[noun] — '[noun] called/of [clause]' — is highly productive for packaging a description into a noun. Here 大科学者になる ('become a great scientist') is packaged via という as a modifier of 夢 ('dream'). 実現する ('realize, fulfill') is the standard verb for bringing a goal or plan to reality; 夢を実現する is a fixed collocation. 大科学者 uses the same intensifier prefix 大~ seen in 大女優, 大成功 etc.