1) She has sharp-nailed fingers.
2) She has sharp-nail fingers.
Which is correct? and Why?
She has sharp-nailed fingers is correct. This is because, by using the word sharp before nails in that format, you are making the entire word, sharp-nailed, an adjective for the noun fingers.
If you use sharp-nail, the word sharp becomes the adjective only for the noun nail (the hyphen has no use then). So the usage of another noun consecutively after nail, becomes incorrect.
Source : Link , Question Author : T2E , Answer Author : Wonder