There's a story that I read that's kind of haunting me. I only remember fragments of it, though. What I remember:

1. The family moves into a house that has some sort of history.
2. The (high-school age) main character (girl? T-girl?) becomes friends with a neighbor girl.
3. Sometimes something scary happens and the main character suddenly doesn't see her friend and the world outside is dark and she's running from something. Later, when things go back to normal, the friend, worried, asks the main character what happened, where did she disappear to.
4. Mother of the friend is into Irish magic/religion and helps them solve the mystery.

Does this ring a bell with anyone?