If you treated it as if it were livestock...which afterall the BB is sort of livestock....either placed in bags or a tub in aquarium water, boxed with polystyrene protection inside and shipped overnight, leaving dispatch as late afternoon as a shipper allows, with a guarantee of a before noon next day delivery, it should be OK
If you paid for overnight with a before noon guarantee delivery and marked the box as livestock, it would be handled more gently but you would need to keep the media very wet...not sat in a puddle per se but straight from your aquarium, don't wring it out, into a tub or bag (if bagged, use two bags to prevent leakage), seal it soaking wet with a small amount of excess water it should survive the journey
Have your sister get some booster just to maybe give it a bit of help to get going again and to revitalise it on arrival if needed.
As long as you pack it very carefully and keep it very wet and warm (warming pack and/or polystyrene), it should be fine.