In the current political climate, that may well be good legal advice. And she has every right to take it and may be wise to do so. But that's a decision that simply is not consistent with her remaining in her job. Whether or not she should be fired for whatever she did in the scandal itself, deciding to take the fifth means she needs to be removed from her position.
I was chatting with people yesterday who said that civil service protections may make this extremely difficult or even impossible. That's something for the new interim director of the IRS to figure out. One way or another, under the present circumstances, someone who is taking the fifth can't be in charge of the division at the center of this investigation. I hope the incoming interim chief gets that.