This is the first time Shiratsuyu-sama's shown that she sees Yui as another one of her kids! I always thought it was weird that she was shown to be still be attached to her former kids after they grow up in the first chapter (assuming that her talking to the phone in the first chapter wasn't her talking to a chatbot but waiting for texts back) and she CLEARLY has obsessive and attachment issues, but we haven't seen her act that way to her shrine priestess.
I hope we meet some of the other kids she raised soon
