Told her that we can't really control what other wish to behave but we could manage ours. If we see our emotions as waves, we should try to manage it and smooth-en it. She tried my suggestion and every time she reports to work, she would just refrain from looking at them ( averting the arising of negative thoughts) and just head for her desk. At first she mentioned its hard, months passed and she has made it a habit. Now she feels that she is far more happier.
Another colleague of mine that likes to post negative comments but now trying very hard to post positive ones. She said its not due to my nagging but I only cares that I am seeing something trying to be positive :) Now her friends read her positive comments and thought she was sad......
Rubber band theory: When we try to stretch a new rubber band, it will snap back to shape. But prolonged period of stretching it, this rubber band will turn soft and eventually does not snap back to its old shape. The rubber band could just be the bad habits we have and needs the stretching.
Sometimes, its really not looking for 101 methods to make us happy but just consciously aware of our emotional swings. And being positive is not just to feel good, but its a more efficient mental state to be in :)