The fundamental flaw in "pedophilia" is that it is so arbitrary. To cite life expectancy, for example, would mean Alucard should be going after women in their 100s (considering his physical age). If an 18 year old has sex with a 15 year old, that's pedophilia. But if a 15 year old has sex with a 10 year old, that's just bad parenting. It's completely arbitrary (although under 10 is definitely probably too young). Technically, if they're ovulating, they're doable.
And I still stand by my argument that Alucard is too old for Maria. Just because a young girl is infatuated with him, her obligations should lie with Richter... ... At least he's human and less than 100 years older than her.