So, I've been working with or providing admin support to a person I work with. They are a professional grade (medical). At the start (4 years ago) they were so nice to work with/for, really clicked and we had a really good work relationship. There was a few times were this person had made the odd comment about other work colleagues of mine that I work well with. These comments would be of a snide nature, and would have been made in passing so I never said anything. So 3 years on and now the comments are awful, a new person started working in the team, excellent worker and very nice person and this has made the green eye monster come out in my other colleague to the point that I've had to say that I do not agree with the derogatory remarks being made. So now things are between not speaking to me for days to being so nice to me it's sickening but within a hour back to making derogatory comments about other people I work with. It's like they just can't help themselves. I'm finding it exhausting. I'm at the point where I do my best to avoid having any type of conversation which is difficult as we work quite closely. I just don't know how to nip this in the bud. Today has been the worst. I cried on the way home from work with sheer exhaustion. It's completely draining and everyone around us in the team thinks this person in wonderland (to their face) but what they say as soon as someone is out of earshot it's a totally different story 
anyone experience of this type of situation?? Thanks for reading this far 