Yes leave her inside where her environment is controlled and she is not at risk from predators. Honestly with you leaving having someone else come into to this situation to try to give her care is going to be very hard when they do not know what they are doing. She may not make it another day much less until you get back. While keeping her hydrated is important I think the shower may be too much for her as well. As you have learned they aspirate water very easily. If the person is able to try to continue to give her water then that would be good.
I know this is stressful and hard. But she is pretty far gone right now. As
@Syreptyon said her eyes are more then just dehydrated.