Yeah, but, WHY? She specifically does it to not become a vampire, that's not just apparent it's explained. So why kill herself for no reason when we could just hand her a holy water and she wouldn't become a Vampire anyway??????
Perhaps Evelyn felt that she was too far gone to be cured? Sometimes game logic needs to be ignored for the sake of the narrative. Evelyn needed to die so that Lucy could join Mila later in the story. Its a lame explanation, but it is what it is. ¯\_(ツ)_/¯
To be blunt, if she needed to die, then kill her. Don't but a character in a position where they are easily saved in seconds and then say no when we try to save them. Just kill them outright.
