Co-workers who cause you stress?

I work in a high stress environment. On top of this are some co-workers that cause me stress for some reason. Particularily the ones that seem very loud ad 'emotionally labile' who dont hesitate to display their emotions loudly and negatively at times. there is one who also emails the manager about every little thing. I am afraid that she has her own 'perfect employee' agenda, and will bad mouth others (she does this in talking) about every little mistake, whether real or in her opinion, sometimes making something out of nothing. She thinks she is perfect and better than everyone. I can't take this anymore, too much drama, and last time she emailed the mgr, it was about something i had been involved with, she didnt ask my input, ect I told her i was upset, that she didnt respect my input, that that was HER opinion, and I had mine. She reacted defensively, and basically was slightly condescending and told me i was too sensitive. was it right to tell her this, or do i have a stress