AITA for selling our childhood piano after my sister said she wanted it someday?

Our childhood piano stayed in my garage after our parents downsized. My sister said she wanted it “when we have a bigger place,” but never gave a date.

After three years, moisture began affecting the keys. I asked her twice to arrange storage. She said moving it twice would be wasteful and asked me to wait until next summer.

I sold it to a music teacher for $300. The teacher collected it the next day and planned to repair it for students.

My sister offered to pay $500 after learning it was gone. She says I knew “someday” meant the piano was emotionally reserved, not abandoned. I say an indefinite claim did not include free climate-controlled storage I did not have.

I split the sale money with her. She returned her half.

The piano is being played instead of deteriorating. That practical outcome is real. So is the fact that I chose a fast sale partly because I did not want another summer of negotiation.