I like
Bethany (knew a very nice one) and I don't think it's too religious. That aspect can be played up, though, in combinations like
Bethany Abigail,
Bethany Noelle,
Bethany Ruth, etc. On the other hand, I don't think combinations like
Bethany Carys,
Bethany Liv,
Bethany Tamsin sound religious at all.
The
Bethany I knew did not go by "
Beth", but I'm guessing that's the most likely outcome. You could try for
Bethan. :)