Agathe is troubled character, tormented soul constantly haunted by her dark past.

She's rejecting, pessimistic, anxious, somewhat paranoid, grumpy and looses her nerves easily. She's got rather aggressive vocabulary and if annoyed enough she may turn to be violent even physically - and it doesn't always take any effort to get her irritable nature to that point.
But no matter how mean or even dangerous Gathe may be, she's not really malevolent, just broken inside. If it happens that she hurts someone more or less badly (let alone kills someone), she will qualm greatly. Deep down her feels and sense of moral is good and at least almost normal, totally different topic it is with her self control and sense of reality. Gathe won't admit it to herself, but she longs for positive contacts, for friendliness - for the good side of the world, that's so unfamiliar with her.

As said, Agathe's past was dark. She was born to home kennel of a responsible breeder, but ended up in puppy mill. For years she lived in poor conditions, forced to have many and many litters of pups she wasn't able to love. Those times scarred her both mentally and physically and chained her with shackles that she can't get free from though she now makes her life elsewhere.