I have had more than a few of those situations. I work in a job where insecurity can run rampant and, for some reason, it's encouraged by the higher ups. My guess is that those kinds of people are easier to control. One big example that I had was where a former friend began to get increasingly defensive when I offered suggestions about things. Long story, short, I was warned about her behavior from many people prior to her transfer to my area. I told her I had heard things, but she started with a clean slate with me and I took her under my wing for a year to teach her the job. After the year, she began to display some paranoia that I was out to get her and decided to beat me to the punch. I began discovering daggers in my back and wondered what was going on. She sluffed off a project for 11 months with a 12 month deadline and I completed it while she took a month vacation. She lost her mind when she got back, accusing me of "stealing her work." It all went downhill from there. Even benign suggestions on my part were met with extreme defensiveness and accusations. Finally, our idiot boss assigned us the same project. I forged ahead and my former friend laid into me, again accusing me of stealing her work.

From that point on, I withheld any opinion, suggestion or shred of advice, watching her fail repeatedly with a smile on my face. Oh, you didn't know that you needed the such and such form to submit? Darn. You didn't complete this part of the project because you were playing kissy face with the boss? I saw it, but I didn't want to bother you.

At least I got to watch her implode and blame everyone else.