Total failure of the safety net that was supposed to be your preceptor. There is no way in hell I wouldn't step in and teach what to do in the event of a hypoglycemic patient. We have a very standard protocol when a patient's blood sugar falls below 70, and I wouldn't expect even a seasoned nurse to know exactly what is expected. There are specific ways and places you have to chart and you also HAVE to call the on call MD to discuss upcoming insulin doses as well as a review of the IV fluids. I would imagine that most people would hold the long acting insulin just because hypoglycemia presents a much more immediate threat than the possibility of hyperglycemia later. In my opinion, that is something the doctor should decide. If it were me I would hold the medication until the doctor gave me the go ahead to administer.
If you are in trouble for this I can't imagine that the other nurse is going to walk away either, not that it makes your situation better, but they are making you feel solely responsible even though they have to realize they messed up too. I am sorry that this happened, it wasn't a good experience for anyone involved, and I hope that they do try and make this a learning opportunity for nurses and PCAs on the floor.
The only other thing I can say is many people have different presentations for low/high blood sugar. Some people only start to feel off when they are dangerously low, while others are completely out of it the moment they drop below 70. It isn't good enough to just ask how they're feeling, you really need to check their blood sugar to make sure they're out of the woods after an episode like this.
Good luck to you.