I'm going to guess they say she went away to die but began trying a trial drug that seems to work.
They won't make this too complicated. I just dont how she got poisoned and survived without anyone knowing. Maybe Brad helped her? Was he out of prison when this happened? I cant remember.
He was out of prison. Selina Wu hated Britt and tried to shoo her away from Brad. Britt refused. Selina brokered a deal with Sonny that Brad could stay in PC and not be harmed. Michael wasn't okay with it. That's why we got this scene at the MC where he told Brad: "Never speak my son's name or I'll end you!" I died laughing b/c CD just can't pull off menacing.
Also, Britt and Brad sang karaoke at her birthday party. That's the night she "died."