What's "the shadow"?
I think fruitbonbon has given some pretty good pointers as to where to start. You can get psychoanalytical and cultural (ie ones reflecting/challenging 'the world outside the text' eg feminism, marxism, historicism) readings out of most of her poems, and a lot of them also have religious issues you can discuss too. I don't know about what fruitbonbon said about not being particularly feminist-influenced though-- I mightn't call Harwood a 'feminist' per se, but she definitely had a strong interest in gender issues and that's reflected in most of her poems.