。
Not only is she clever, she's beautiful too.
Literal
She [topic-は] clever just-not-only beautiful.
~だけでなく ('not only X [but also Y]') stacks two predicates of praise. With a na-adjective base, the form is 聡明な+だ→聡明なだけでなく, with the implicit copula absorbed into the conjunction. The frame is productive for combining traits in praise or criticism: 美しいだけでなく賢い ('not only beautiful but smart'), 安いだけでなく品質もいい ('not only cheap but high quality').