AITA for breaking my sisters nose to prevent her from harming my pets?

A 17-year-old girl caught her 13-year-old sister trying to force her way into the pet room while babysitting. The younger girl openly admits she wants to kill people and animals, feels no remorse for slaughtering wild birds and squirrels, and has written disturbing, detailed plans to hurt her big sister and the pets.

When blocked, she bit down viciously, requiring stitches. In response, the older sister punched her nose to break the bite, pinned her against the wall, and called their mom to pick her up. Now mom is furious, branding her the asshole for striking her little sister.

‘AITA for breaking my sisters nose to prevent her from harming my pets?’

It all happened while the 17-year-old sister was babysitting her 13-year-old sister at home:

After the severe bite, she had to be taken to the emergency room:

This boils down to a big sister using force to stop her troubled younger sibling from reaching animals she clearly intended to harm. The 13-year-old’s history—killing wildlife without guilt, graphic violent fantasies—lines up with serious red flags for conduct disorder, especially the callous-unemotional kind where empathy is missing.

On one side, hitting a child, even a violent one, feels wrong to many, and mom sees it as straight-up abuse from the older daughter. Society generally draws a hard line against adults (or near-adults) striking kids.

But psychologists point out that repeated animal cruelty at this age is a major warning sign. According to experts at Psychology Today, intentional animal harm in teens often ties into broader antisocial patterns and demands immediate intervention—ignoring it risks escalation. The Child Mind Institute notes that kids showing callous traits lack concern for others’ suffering, which matches what’s described here.

Legally, pets count as property in most places, so reasonable force to prevent imminent harm to them can be defensible. Once the bite happened and stitches were needed, it crossed into personal self-defense territory, making the response more understandable.

The real fix isn’t debating who hit who—it’s getting the younger sister evaluated and into therapy fast. Authorities like child protective services should be involved if the home environment isn’t addressing this. Family counseling could help untangle the custody and mental health mess too.

These are the responses from Reddit users:

People online had strong feelings about this one, and most came down firmly on the side of the 17-year-old.

A huge wave of support poured in for defending the pets at all costs, especially given how dangerous the younger sister’s behavior sounds:

Many commenters zeroed in on how urgently the 13-year-old needs professional help, while slamming the mom for downplaying everything:

A couple of darker, sarcastic takes popped up too:

This hits hard because it mixes family chaos, pet love, and scary warning signs in a kid who desperately needs help. The older sister chose to protect vulnerable animals and herself, even if it turned physical. Most people online back her, but the deeper worry is what happens if nothing changes for the 13-year-old.

What would you have done in her shoes? Is there a non-violent way out, or was this the only option? Drop your thoughts below—we’re curious to hear where you stand.