My cat of 2 years went to heaven today

2-3 months ago, she was diagnosed with B1 Heart disease and the doctor didn't prescribe meds or do anything since it hasn't progressed a lot at all. However, after running around she started having episodes where she would breathe very hardly and open her mouth and sometimes unaware pooping but after a few mins she is back to normal. But yesterday, she had an episode again but it was worse, she started rolling around and had sounds when breathing so we brought her to the vet and admit her to the hospital. The doctor said she was getting better and this morning she could even walk. But a few minutes after the walk, she started getting worse and died peacefully in her sleep. We are so sad because she was still so normal before running around yesterday and she isn't with us anymore today. And I couldn't be with her when she was dying. :(