My book says that 'shadow' is a tricky word; the phrase "the shadow of a girl' implies that the girl is so upset/unhappy/depressed/rundown etc that she can be compared to a ghost. Is that really so?

I don't mean that this structure cannot be used figuratively - of course it can - but something tells me its usage isn't limited to it.

To put it in a nutshell, can I use phrases 'the shadow of a girl" and 'a girl's shadow" interchangeably?

Thank you in advance.