。
She isn't actually as young as she looks.
Literal
She [topic-は] appearance to-the-extent-of actually young not.
A textbook outing for the AはBほど~ない pattern, 'A is not as ~ as B.' Here B is 見掛け ('outward appearance'), so the comparison is between her real age and how old she seems. 実際に ('actually, in reality') is technically redundant given the construction itself, but Japanese often layers in this kind of emphasis when contrasting impression with reality. 見掛け and 見かけ are interchangeable spellings; the kanji form 見掛け leans slightly more bookish.