I would use a disposable glove, and lubricate a finger, then insert it 1-2 inches inside the vent to feel for a stuck egg or an obstruction or hard droppings. Make sure that she is drinking plenty of water. If you feel an egg, give some ground egg shells or a calcium tablet or Tums in some yogurt or food. Soaking in warm water can help an eggbound hen lay an egg, unless the hen is very sick.