。
She takes pride in her daughter.
Literal
She [topic-は] her own daughter [object-を] pride [as-に] is-doing.
自慢にする ('to take X as a source of pride') uses the productive [X]を[Y]にする pattern — 'treat X as Y / make X into Y' — to frame the daughter as the focus of pride. Slightly more emphatic on the act of holding-up than the bare 自慢する. Common in describing settled, ongoing attitudes (note the ~ている).