Initially, i thought it was not right for the employers to fire the lady just because she expressed how she felt about he coworker. But then again, i think the woman chose a wrong method to express how she felt about her coworker.
The employers did not provide any reason for firing the woman except that she was harassing her coworker - which they called "quote harassment." 
According to the expert's interview, the woman was legally fired; like the expert says: the best rule of thumb is that if you do not want it to be on the front page of the newspaper, never type it on your keyboard. also, according to one of the interviewer, "never put anything in writing that could come back and hunt you." i think the word digital footprint means that one might think that he or she is doing something on the internet privately when actually its not private. the person might either be tracked by an unknown person who is trying to look for something bad about the person. Digital footprint can also me leaving vital information about yourself or about a person that one can easily trace them.
the things one post on social networks like Facebook or twitter can be private or not depending on the mood the person activates in regard to that status or post, or depending on the system the person uses - if it is private or not.
If i was a friend to the woman, i would have advised her not to post such because personally, i do not think it is right for everyone to know what is bothering you or what challenges you are facing on a social network like that.