(A) She was a child prodigy, and Clara Schumann

Alters the meaning. According to this, Clara and the child are two different people,which is not the case

(

B) A child prodigy, Clara Schumann

Here the modifier " A child prodigy" describes Clara and also this is Not wordy

Child prodigy that she was, Clara Schumann

Same mistake as in A. because this deals with two different people rather than one and the same.

D. Wordy

E. Does makes sense, but if we have to chose between B and E, so better go with B(less wordy)

IMO

A) She was a child prodigy, and Clara Schumann
>> And signifies parallelism. Clara....parallel to what ?

(B) A child prodigy, Clara Schumann
>> Correct

(C) Child prodigy that she was, Clara Schumann
>> that tells more about the verb prodigy....prodigy cannot be she was....it has to tell something....which it is not telling.

(D) Clara Schumann has been a child prodigy, and she
>> Has.
(E) Being a child prodigy, Clara Schumann
>> Being.