Can you give an example of when an interpreter may not be objective?

For example, suppose a school system employs an interpreter to work with a Deaf child in a classroom.  Now suppose that she is asked by her Principal to interpret for a Deaf parent during an appointment where the parent is very upset about an issue.  Imagine that the parent proceeds to cuss out the Principal. How difficult that scenario might be for the interpreter. She doesn’t want to jeopardize her job by saying all those things to the Principal. But if she doesn’t – if she “sugar coats it” – that is unfair to both sides.