、。
Though she was a child, she wasn't afraid.
Literal
She [topic-は] child was [but-が], was-not-fearing.
恐れる ('to fear') in the ~ていない form means 'is not in a state of fearing' — the absence of an active fear response, rather than the lack of fear as a personality trait. The は inserted before いなかった adds emphasis or contrast: 'was not [in fact] afraid.' The mid-clause が pivots into the contrast: 'was a child, but...' であった is the writing-style copula past, more elevated than the spoken だった.