This seems very far removed from translating each word literally: "She touches flute since small". How many contexts can tocar be used in?
Tocar can be play an instrument or touch something/someone
Simply "tocar" can always be used as playing something as an instrument. That is why we often add the "em" (toca em, toca na, toca nos) after the verb when we mean "touch".
What is wrong with: She plays the flute since being youg?
Would "She plays flute since little" do it?
She has played the flute since she was small—seems right to me.