Silver Moon Pack has Nathan's spies all over the place. He could be watching Cecelia's every move. She becomes upset and unappetizing for no reason, which will lead to a result that Vivian will leak anything if one of Nathan's spies set a trap on her.

It’s not that Cecelia didn't trust Vivian. On the contrary, she was only too aware of Vivian's lack of scheming to have such a worry. Cecelia doesn't want to take any risk with someone as sophisticated as Nathan.

In particular, this risk is directly related to her life and Damon's safety.

"Vivian, I... I'm changing my clothes. You go down first, waiting for me...