。
She is afraid of her own shadow.
Literal
She [topic-は] her own shadow [at-に] is-frightened.
おびえる ('to be frightened, to cower in fear') takes に for the source of fear — '(she) is frightened of X.' 自分の影におびえる is a literal rendering of an English-style idiom ('afraid of one's own shadow'), used to describe extreme timidity or paranoia. Whether it parses as a recognized expression or as a fresh literal image depends on the listener's exposure to English idioms; it isn't a native Japanese saying.