I noticed that she mentioned at least once or twice on her Vampirefreaks page, when she was still a minor, that she would be a young age (like 15), but act “older” for her age.
That’s the same phrasing that other young girls on the Internet at the time received from predators, when they were being groomed.
I’m not excusing Mei’s actions, but it’s possible that she started to turn on to her weird fetishes because a grown adult was talking to her on a website like Vampire Freaks.
It doesn’t seem like she had a lot of parental supervision on the internet.