Let's say huntress and snivy are both infected:
Huntress may kill one of us:
Kill me - you die, plague win
Kill you - me and plague (tie or plague win)
Kill ghost - me (wolf win)
If huntress is dying but snivy is alive:
Kill me - snivy and plague (tie)
Kill you - snivy and me and plague (three way tie)
Kill plague - snivy and me (tie)
If they both live, it's a town win, unless somehow i convince plague