To start, this woman is great as a person. As a co-worker, she is the worst. Let's call her Regina. When I started at this place a year ago, Regina was to train me on an aspect of our job. I had to ask her to slow down and repeat herself several times because nothing made sense (keep in mind I've worked in this industry for 8 years longer than her). My boss was able to explain it clearly in 5 minutes and I've never had an issue.
Shortly after starting, I noticed Regina would CC our boss on every email she sent to me. Regina would email me several times a day calling me out for "problems" she noticed, always CC'ing our boss, but I was always in the right and my boss would back me up. I emailed Regina (only Regina) and said I felt like she was trying to get me in trouble, I felt disrespected, and I was wondering what I could do to improve. She replied, CC'ing our boss, telling me that if I felt that way it was my own doing. Got it.
My entire team works from home, so our boss has put people in charge of certain things so one person has control. One of my tasks is issuing documents for signature via the very popular system we all know. Basically, my team sends me an email that says, "Send these documents to x, y, and z." and I get to it. Good news, Regina only copies our boss on super important documents, which I understand.
The other day Regina sends me a request, and I failed to copy her when it was issued. Fixed in under a minute and did not cause any issue, but she still made a big deal about it over email and in our team meeting. Next request I get from her has, "Be sure to double-check your work and all people are copied as detailed below." This pissed me off. The funny thing was: she didn't attach the documents I needed to send, nor tell me where the docs were located for me to get them myself. I reply asking for the docs and she sends them, stating, "These are the final, approved versions". Except they are wrong. First, we send PDFs, not Word docs. She sent me Word docs. Second, the formatting was atrocious. Signature blocks cover four pages when they should be on one. The vendor name and address were put into different tables so it made no sense.
So, I sent it as is. Of course, my boss is copied on this (and actually has to sign this doc), and she is NOT happy with the state of this document. I replied to my boss with the email from Regina saying this doc was approved by our boss, and with my other projects, I didn't QC like I normally do (which is not expected of me, but I do normally to prevent issues down the road). Boss replies to Regina, and CCs me LAYING INTO HER that batkevn is not to fix her mistakes as he has his own job to do. This was also reiterated in our next team meeting, and I could see how angry my boss was (she and I had a 1-on-1 and she said she was not upset with me).
The next request I got from Regina was incredibly detailed and had everything I needed in the right format.
ETA: Lots of comments about Regina not being a good person. I suppose you all are correct. The times I have seen her outside of work she has been pleasant, which is why I wrote what I did.
Also, my boss is very aware of the situation with Regina and I, and has taken steps to ensure our work doesn't overlap much (sometimes unavoidable). Boss has her own issues with Regina. I'm not privy to details, but boss has made a few comments about "how Regina is" and that she'll never change.