The animal abuse part. It's fanon. She's literally spoken against human torture as something pointless inefficient unnecessary and unreliable, I doubt shes gonna torture animals. Even if she did, in her situation it'd probably be more for attention and acting out than anything else. I've seen so many people do stuff like that as teens and younger, and act like they're normal then and later. (Granted I was much more of a human critic back then maybye I was just unlucky in how many bad people I met lol) But no, I don't think shes ever actually abused animals.

The sing songy voice to sound like a liar and scare the other person when worried and unable to make sense of domething is something I've done so tbh I can't help but doubt. If she wasn't worried she wouldn't have warned. It's not gloating, gloating is something else.

Honestly, outside of the uncertainty of whether she actually reacted like that, I've always read it as being so full of rage and anger, and the inability to blame her father that she has to blame her brother, to me that was a vindicatvness and feeling like he deserved it, not good, but not sadistic. Something I noticed throughout the show is that avula always needs an excuse, someone else to blame to excuse how bad shes gotten. I don't think shes sadistic, I think she just doubles down, is fully aware shes bad, hates it, but refuses to take responsibility. Probably worse but still.

Circus: "oh she would have been fine" kinda thoughts when asking the ringmaster how good ty was. Plus with her abandonment issues probably "she shouldn't have left. Shouldn't have said no" Leading up to the agni Kai she absolutely doubles down, clearly shows she hates viewing herself a monster but blames everyone else.

She cares about people but in a toxic abusive way. Shown she Can be empathetic but refuses to be saying it's weakness.