I actually have high hopes that her BBL wont look absolutely terrible. Most women I've seen getting BBLs are fairly skinny with slim thighs, while Arietta is curvy with nice thick thighs, so the proportions and "ass to thigh ratio" might be good, if she didnt go crazy with size and go full Kim Kardashian, diaper looking ass.
Don't get me wrong, I loved her natural ass, and in my opinion 99,9% cases of plastic surgery are a huge downgrade, but let's wait and see how it actually looks.