I've been trying to figure this out, as the film never establishes whether or not vampires are capable of breeding. We know that she is of Lee's blood, so it's just a question of whether or not her mother was human.
Just when my coil's reaching the green line... - Shotaro Kaneda
In Mr. Kikuchi's VHD universe, vampires are capable of breeding with either other vampires or with humans. Either mother or father can be a vampire--the result will be a dhampir child. Vampires can also be created when one bites a human and wishes them to change. But born vampires consider themselves superior to converted vampires. I haven't watched the movie in a long time, so I'm not completely sure what the deal with Lee's daughter is there. But in my translation of the first novel (available now from Dark Horse comics!) she was a vampire, not a dhampir.
In the film,she is a Dhampir but not in the book. In the VHD universe,Vampires are capable of breeding with each other and with humans-he uses a more biological scifi basis for his vampires. It is also interesting that they have synthetic blood widely available in D's world,so all the blood sucking that goes on is completely a perverted habit of oppression and lust rather than a necessity for life for these Dhampirs and Vampires alike! Knowing that the Vampires are doing all this for sadistic reasons adds to the righteousness of D's quest in the books.
She's a Dhampir since her mother was a human although oddly enough, she doesn't know that and is shocked when Lee finally tells. So it seems it's possible to be a Dhampir but more Vampire than human, unlike D, who's half-half.
When darkness overcomes the heart, Lil' Slugger appears...
i don't manage to get the original version, but in the french version, the answer is not unknown as D. said to lamica, when her father died, that she got no need to die as she's a dhampir like him and not a vampire...