She's been locked away for so long that she has no/little knowledge of the outside world.
Much of her speech is quite degraded.
Before being locked away she was formerly a more fearful/animalistic demon however after her memories and the majority of her powers went, so did her previous form.
Nobody knows what she looked like during being sealed but when someone broke the seal, she took the form/characteristics of the first thing she saw but parts of her form lingered.