Hang in there!
Time management is something that takes time and your educator should know that.
I think your preceptor is just trying to cover her butt over that IV bag being run at the wrong rate. She is responsible too, she should have been there with you when you hung it since it wasn't right and she was aware it wasn't right and it was your first day in the level 3 nursery.
I'm surprised the pharmacy didn't send a new bag, that is a huge issue to try and figure out and it would have been safer and easier to just send up a new bag. Also, some meds are caustic and to send a double concentration freaks me out. I am a pain in the butt when it comes to stuff like that, I insist that things are the way they are prescribed, pharmacy has never gotten upset when I ask nicely. We are the baby's advocate and it is our butt on the line. Just think about this, the pharmacist is pretty sure that something is ok and tells you it should be ok on the phone. If an untoward result occurs and it wasn't ok do you think the pharmacist is going to say, oh yeah, I told her on the phone it was fine. It would be more like, oh, I don't recall talking to her, I don't think I would have said it was ok to give that med if I wasn't 100% sure it was safe. I don't look at the world in a cynical way, but when people are up against a wall and their livelihood is at stake they are going to go into self preservation mode. I think that your error was the culmination of many errors starting at the pharmacy and ending when you hung the bag.
We have a policy in my unit that 2 nurses have to check all IV bags and lipid syringes against the order, then 2 nurses have to sign off when you do a tubing change, bag change, or rate change. It takes a few extra seconds of time, but the peace of mind is worth it. This change came about because of an incident that happened a few years ago. This is what incident reports are supposed to be for, when something untoward happens, the powers that be can investigate and if there is a pattern of incidents then they can come up with new ways to do things so that the errors don't happen. Incident reports aren't supposed to be punitive and I am sorry that it appears this way.
I am a new grad, I am a couple of months away from completing my first year of nursing. I am just now starting to internalize time management and prioritizing. Handling a 4 feeder assignment is very time consuming and shows that you can manage your time. I run more when I have a feeder assignment then when I have sick kids.
Keep on keeping on, learn from all mistakes, yours and others. I think it is awesome that you have such a long, phased orientation.