religious teen placed in foster family

I read this sometime in the '90s--not sure if it was early or late. I remember only the smallest snippets of this book.

A teenaged girl has been removed from her family, who are members of an extreme religious sect--because her parents are being investigated after one of her siblings died of a preventable illness. The story takes place in the home she's living in. There's a girl about her age who thinks she's weird and a (single?) mom. The point of view shifts between these three characters. I think there was a lot of tension in the home.

I remember that the girl is always talking about how "the big cat's coming and coming soon," and the family thinks she actually means a cat, but that's the shorthand her community used for the big cataclysm, the end times.

At the end of the book, she gets to go back and visit her family and realizes that they really are kind of messed up.

Thanks for anyone who can steer me in the right direction!

That summary sounds really interesting, but I'm afraid I don't know it. Good luck!

It's from 2002, but I'm fairly sure that this is The Book of Fred.

That is definitely it! Thank you so much.