If father deceased, what do you do to be able to help represent your mother before IRS for income tax?

My parents were married and joint filers, with my father signing as the main filer, and my mother signing as the spouse. My father is deceased, and if I want to be able to go in before the IRS in case my mother needs help explaining a tax, is the Form 2848 the way to be able to get permission to represent her? I've called the IRS but different people give me different answers. Some say I can, but another person said I can only represent her if I'm an official tax preparer from a company. That didn't sound right - then why this Form 2848? Any tax buffs out there who have done this? Thanks in advance...