My parents had gotten her when I was a year old. She had chosen me as her favorite human

My parents had gotten her when I was a year old. She had chosen me as her favorite human, and even as a baby she would stay close to me.
Over the years we grew closer. She became my best friend, I told her everything. All she expected in return was my bed and chin scratches.
Life was good, then one day we took her to the vet. Sabrina had a rare heart disease, we could not afford the surgery, and we accepted that she would only have a year left on her life.
Three years later she became extremely sick. I did not notice before it was too late.
I woke up one morning to begin preparing for school. She was coughing and having difficulty breathing. My mom hopped in the shower, and we were getting ready to take her to the vet.
As I waited for my mom, I sat there with her. We were on the steps and she looked so pitiful. I petted her, and talked to her. Her eyes became glassy and she passed away.
It was the hardest goodbye I have ever had to say to a pet. I held her as she passed away.
This was the first time I had lost something I loved. It hit me hard. I grieved for months.
Sabrina was a once in a lifetime cat. I still miss her, even three years after her death.