Is Danielle really dark danny's daughter?

Technically speaking, she is him, being his clone.

well theres 2 daneills . one Vlad made with cloning and science and one dark dany had with Mandy.(afterbirth) "Dark Danny" is made of both of what was left of Danny phantom when he removed away his morals and humanity with special claws. (friends + family died so he wanted to escape the pain) and also he is Made from 1/2 Vlad.

but its еще like danny just absorbed his evil to transform himself. because he looks alot еще like an older danny with vlads powers than he does a equal fusion of the 2 chracters also he identifies himself as Danny most of the time. but basicly the 1st. dani was made by Vlad but with 100% of orginal danny DNA. the секунда danielle(afterbirth) is like 25% danny 25% vlad and 50% Mandy.