Looking for a fiction book about astral projection, and a battle between the girls father and the cult leader?

Question

Can anybody help find the title of this book???
Many years ago (perhaps 25), I read a paperback novel that I'm trying to find.
It was about a girl who was abducted by a cult. The father began investigating and found that the cult leader was an expert in astral projection. The father then goes to a master who teaches the father all about astral projection.
The father tracks the cult leader and in a very supernatural ending, he does an astral projection battle with the cult leader, where they both inhabit inanimate objects around them and use the inanimate objects to do physical battle. If one can cut the other's 'silver threat' that connects the astral self to the physical body, the physical body that has been cut off will die. At one point, the cult leader, for example, inhabits a teddy bear and brandishes a knife to try to cut the astral connection of the father.
The cover of the old paperback had a teddy bear with glowing red eyes, holding a knife.

Answer 1

I did some research on this and it looks like it might be the book called Double Trouble by Barthe DeClements--though you didn't mention anything about twins, the review does talk about astral projection and the cult. It was also first published in 1988 but the cover of the book wasn't available for me to see. It's considered a Young Adult book. Hope this helps. :)