Power
Margo had been moved to a room next to Antione. Cora had him take some of Margo's belongings there too so that she could shower and function. This had the unintended consequence of Margo thinking Cora was attempting to leave her.
It had been a full day of Margo in instinct driven crazy mode. Cora had to sedate her one other time and threaten it two other times besides. Margo was trying to attack Cora, but she didn't understand to what purpose.
Finally, Antione explained that Margo was very old which meant that she was from the time when there was always a dominant mate. Margo's instincts said she was the obvious choice. She wanted Cora to submit to that dominance.