what else can u expect from someone who came to fully accept being born and raised solely to be given up as sacrifice in place of someone else. any person would have to be broken somewhere after that...
Saliphie in a weird sense is trying to find purpose in her life with these self destructive tenancies. As a sacrifice, she had no worth other than to die, so for her there's nothing really left to lose. She doesn't have a place in the human world anymore and she's already decided to dedicate her life to the beast king. That includes does what's best for his people. She sees as her duty to the king and his people even though there are probably much better ways of gaining the people's favor.
Ok about Saliphie. She is in a depressed state in most of her close ups. She looks like a doll drained of life. Plus she has all these self destructive tendencies. And I know it's because of her up-bringing but she suffers from at least depression. I mean there must be more mental illnesses that aply to her. Moral of the story - poor Saliphie.