Elizabeth had been observing Savannah and Charles. Noticing that they had gone behind the closed door, she made them tea and used it as an excuse to enter the room.
Before she knocked, she stood at the door and listened to what they were talking about.
And it seemed like they were having a serious discussion about killing Valeria. Elizabeth heard Charles telling Savannah about his vicious plan.
"Get a few guys and dress them up to be waiters in the resort, and they can improvise on how to kill Valeria once they're in there. Those young rich kids attending the party probably won't and do anything to help her. Heck, they probably wouldn't even expect those waiters to launch an attack! That would be easier for our men to leave after they killed her."