I don't know whether the IRS employee is making some kind of political statement about the inquiry or is genuinely concerned about self incrimination in criminal acts, but if I was to guess it would be the former.<quoted text>
Why would a public employee refuse to tell the people's oversight committee what she did or does? Does she deserve to continue to receive a paycheck from those same people that she refuses to tell what she did/does to earn it? Should she be fired immediately?
I don't know if she CAN be fired for exercising her 5th amendment rights, although there are different rules for political appointees and civil service employees.
I'm only casually familiar with the legal precedents regarding exercising 5th amendment rights before Congress, but I think it mostly goes back to the 50s/McCarthy era.