。
She takes pride in her son.
Literal
She [topic-は] son [object-を] pride [adverbial-に] is-doing.
誇りにする ('take pride in / make a source of pride out of') is a productive [noun]+にする 'make into X' construction. The structure [object]を+[abstract noun]+にする lets you express figurative 'turn X into Y' relationships — 誇りにする ('make X a pride'), 友達にする ('make X a friend'), 趣味にする ('make X a hobby'). ~ている marks the ongoing pride state.