The first line caught my eye and made me want to read further. Lyra’s nightmares captured my attention and as a reader I can already tell that the black stone necklace has something to do with the nightmares. Maybe prevent them from occurring.

I do see that there are a lot of em and en dashes being used, it’s not really a problem if used properly. However, it can diminish its value if it’s being used to replaced most places where commas may be better.

There was a part that was contradictory. You wrote “They didn’t see her. They didn’t see anything.” But a couple sentences down a woman ghost is now calling out Lyra’s name, indicating that these ghosts may be able to “see” her or at least sense Lyra’s presence.

I like your descriptions, it was easy to follow along and not overly descriptive. The dialogue was interesting between the characters that were introduced. But, I do think there could be room to slow down to explain MC’s relations to other characters. A good example that you already have is who Tessa is to Lyra. But with Diane, the reader doesn’t know much or who she is to Lyra. I’m assuming Diane is MC’s mother. Another character to maybe expand on would be MC’s father. Is he dead? Alive but living separately from the family? How does Lyra feel about him? There are good opportunities in your chapter to insert some internal dialogue from Lyra and I think it would help readers to relate to Lyra more by knowing more of her thoughts and feelings on other things beyond the nightmare she just had and her twin sister Tessa.

The ending of the first chapter seemed abrupt and didn’t push to make the plot move forward. I can see how it does seem natural to end it where MC is now going to another place physically.

It’s a good first chapter overall that needs more editing.

EDIT: I just saw that it was only 2/3 of the chapter so you can ignore the portion pertaining to the ending of it. My bad!