Sadie? *spoilers*
-Gina gets poisoned by the wine.
-Miguel gets shot from behind by David.
-Choi gets shot by Pruitt.
-Tommy gets slashed by Sadie but manages to survive.
-Will, Kira, and Ben run out together and Will/Kira get chased by Sadie.
-Ben breaks down the glass door and gets stabbed and shot.
-Will and Kira find Sadie bleeding out on the sofa.
So who attacked her? I can only think of Ben or possibly Tommy but I think Tommy was still recovering from being stabbed?