Without knowing the details: Confronting the person (after HR said not to!) was a terrible decision, and probably made the person extremely uncomfortable. Then following up with that person to contact HR sounds like straight harassment. I get that the author may have had honest intentions, but the party that initiated the complaint clearly was uncomfortable with contact. It sucks and it's awkward, but at that point y…
Just think of her as a bully - give her a wide berth while passing her on the corridor, don't stay in common areas when she's there if you can help it, and if you ever get invited to the same party as her by a mutual friend, stay at the other end of the room. Best of all, if you can, quit your job. You don't want toxic people in your life.