That girl Ayumi is only 13, but she's been performing in movies and on stage as a child actress since she was five.
Literal
That Ayumi [called-って] child, still 13 years-old [but-だけど] 5 [time-のとき][from-から] child-actress [as-として] movies [and-や] stage [in-に] performing.
子役 'child actor/actress' — 子 'child' + 役 'role.' として 'as, in the capacity of' marks the role. 出演 'performing, appearing in (a show)' is a Sino-Japanese compound. The sentence conveys impressed surprise at a young performer's extensive career.