Forgive me for posting without a proper introduction! I'll get to that in a second.
I have no experience in this area at all - in fact, I'm just finishing up my last two prereqs and am beginning the application process, so I'm just a lowly pre-nursing student...but I have personally found myself in similar situations in professional settings. I just wanted to give you my sympathy and my support.
I think "covering" for yourself would involve insuring there is adequate documentation of this person's lack of skills - you should be sure you can show that this person consistently gives inadequate care. The disciplinary actions, if any, brought against this person should be shown to be equal to those given to others in similar situations.
Things like this, in ANY professional environment, weaken both the institution and the individuals involved. Everyone ends up walking on eggshells - which can serve to empower the instigator!
I'll be thinking about you. You have my support.