Lets look at it from Leia's point of view, she has lived in that house since she was a kitten right? Thats her domain, she hasnt known anything else. The sudden sight, sound and smell of Onyx in her house would be the equivalent of us waking in the middle of the night to find some one sitting in your lounge, on your sofa, watching your telly
How would you feel? Frightened, angry, apprehensive, defensive? All of those I'd imagine, these are primitive emotions and all ones that cats share.
Surely better to get to know some one before allowing them into your personal space and for me that takes time.