Perhaps because it's been so many days since she was asleep. There has always been a saying not to eat when you're hungry as everything inside your mouth would just taste divine so you could be full. And this was even more true as Arabella found the bread and butter dipped in the milky stew was just so delicious that she could cry tears of joy from it.
But while eating she recalled her conversation with Malvo and about the princesses. At some point she wondered why she didn't feel so energized after hearing what Malvo had to say. She also questioned why Cassius didn't tell any of this to her but who was she to him that she would even dare to ask such a question?
She's nothing to him that's for certain… there is no reason for him to go ahead and explain everything he does especially when he has done it with the throne in mind.