Children of the Night : Did I Miss Something?

Did I Miss Something?

I watched this movie recently and there are a few things I don't understand. The biggest one is the mother and daughter the priest kept locked in the bedroom. They were both vampires…but the mother was drinking the daughter's blood *and* looked like a normal vampire in canon (fish-like appearance) while the daughter seemed normal except for being pale. The daughter also ate leeches instead of people. I don't get it, why the contrasts?