Backstabber

Today at work, I was almost backstabbed by my preceptor right in front of my nose and with my manager around... Kaoz... Damn't bloody pissed off! Dare to accuse me when the fault didn't lie with me in the first place.
My preceptor signed for an injection see didn't give as the patient would only come for the injection on 14 July. But she had signed for it like as if it was given. Thus, my manager came to know about it and questioned her about it. I was also called in for explanation as my name and signature was also on the medication record sheet. (It is a common and a must for all medications given to be checked and signed by 2 nurses. The one who signs on the top column is the one who administers the medication, the one who signs on the bottom column is the one who has checked that the right drug was given.)
So my manager was asking the both of us what happened and how the mistake was made. I explained that I had checked the medication but did not see and hear whom she had administered the injection to as I was busy with my own patient. My preceptor kept quiet and only muttered some insignificant words.
After my manager emphasize the seriousness of the event and requested for an incident report, the conversation followed:
Preceptor: Amelia, I thought you gave the medication and I just signed it for you.
Me (shocked): No, I did not give the medication.
Preceptor: No, you gave the medication and signed the wrong column so I just sign it on the top column. See, you even written the batch number of the injection and labelled the medication form.
Me (pissed and angry): I wrote the form and the batch number for you 'cause you didn't write them down and it is required to be all properly filled up.
Preceptor: Aiyah, I don't know lah!
Me (totally pissed and loss for words: ...

I think my manager could sense my firmness in maintaining my stand in this case that I was not the one who made the mistake and my preceptor had to be the one who write the incident report.
However, I am very shocked as well as pissed at how my preceptor for trying to push the blame to me for something that was actually her fault. This is how some people can be when they need to cover their ass and safeguard themselves. How evil! Luckily, I am firm and fast to react, otherwise, I would be the one in hot soup now...

For the past few weeks, my preceptor has been making many serious mistakes:
1) Taking blood for extra tests wrongly and charging patient extra money for the test.
2) Administering the chemotherapy for a patient is not supposed to be recieving chemotherapy due to low blood counts.
3) Setting the cannula for a patient improperly and causing the patient to get extravasation.

She is obviously not concentrating on her work...