She choked in her sleep most definitely, Check her sleeping area if any newspaper looks bitten into. Or maybe she devoured a full one or two. However, there is a possibility it egg bound because if she was in her normal sleeping position she must've died in her sleep, Its either she choked or egg bound, I would try to contact a vet to confirm because if she DID choke on the newspaper you need to find a different floor filler.She was in her sleeping position
Laying down with her beak touching the floor