Does Jen or any of the other characters have any religious or spiritual beliefs?

I’d say that Jennifer is an atheist, just by default.  God and whatnot just aren’t things she devotes a lot of time to thinking about, and she’s never needed Gods help to solve a problem.

Ten is too young to really care about it either, and her mother never raised with any particular beliefs other than in punching things.

Kaya might have some ‘spiritual’ beliefs, but she doesn’t really practice anything.

Sayuri comes from a Japanese family and they observe some traditions from their homeland.  She herself is the kind of person who reads her horoscope, not because she necessarily believes there are any mysterious forces at work, but just for fun and also it motivates her a little bit.

Doctor Jana Sarkis is muslim, so she’s the only character so far to be a member of any of the major religions on Earth at the moment.  (Doesn’t really play much role in any of the stories so far though, as she hasn’t been in them very much).