To say that he's not guilty becuase of some special feature of the victim is to say that people who are different to the mainstream have a lower level of protection from violence in the law. It also puts blame on the vicitm for the outcome of the violent attack.
If Mr Average Joe gets deliberatly stabbed once and dies, his attacker is guilty of murder becuase stabbing someone is an act that an ordinary person would expect might cause death, even though it usually dosn't (assuming there's no defence like insanty, self-defence etc).
If Mr Heamophilliac Joe gets deliberatly stabbed once and dies, is his attacker to be let off murder just becuase someone else might not have died? If so, the law provides Heamophilliac Joe with less protection from murderers that his buddy Average Joe and thus he is given less protection from attackers by the law.
The only differnence is that the JW makes a choice and the heamophilliac dosn't. But it's a choice she's entitled to make, so the attacker becomes a murderer as a result of his own violent actions - no one else is to blame, and especially not the victim.
We don't reduce the culpibility of cop killers becuse cops put themselves in harms way by their job choice.
As it happens in this case anyhow, the attacker must have known that she woudn't take a transfusion which finally puts rest to any attempt to reduce his culpability (notwithstanding he may have a defence in insanity) on the blood transfusion issue. But it's really not at issue anyway to my way of thinking.
As someone else suggested, just becuse we beleive differently to somone else, we get no discount off the lawful punishment if we kill them.
Max