My sister won't forgive me. What should I do?

Anonymous
I need help on this matter, please.

Last Sunday my older sister went on vacation and had asked me to babysit her dog (A pug) for a week, and it was no problem at all so I said yes. I took good care of her and stuck to the strict diet that my sister had made for the dog and made sure to walk her everyday after work and play with her when I can.

This past Saturday I took my sister's dog out for a walk like I do every morning before work but this time it was different. My sister's dog is very well behaved so like always I walked her without a leash on (My sister walks her like that too) and just let her run off so long as she kept remotely close to me. And, like always as soon as we get to the dog park she would run off and I'd have to eventually chase after her.

This past Saturday though, a much bigger dog (It was a mutt) chased down my sister's dog and started to attack her. I ran towards the fight as soon as I could and physically got in between the two of them. Very soon after the other dog's owner got a good hold of her own dog but my sister's dog was very badly wounded in the fight.

I took my sister's dog to the emergency pet hospital as quickly as I could but she didn't make it.

I've felt like crap and have been seriously depressed about the whole thing ever since. My sister won't talk to me at all; she won't answer her phone, reply to text messages, or even answer the door when I go to her apartment. My mom has been trying to get my sister to talk to me, she even told her how it was breaking her heart that her only daughter was not talking to her only son, and yet, she won't talk to me at all.

What should I do? I feel so terrible about everything and I don't know what to do. Will my own sister go the rest of her life without even talking to me? What would you do? Please help.
My sister won't forgive me. What should I do?
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