That's a shame they are keeping her overnight. Is there anyway you can bring her home late that afternoon? Will there be someone at the vets overnight, because otherwise I don't see the benefit of her staying. Ruby's vet didn't require an overnight stay after her spay and I know many others didn't have to stay either.
If bringing her home is not possible, I would leave an something of yours with her, something with your scent like a t-shirt possibly.
Good luck and keep us updated!
