No, dont feel a bit bad about the steak. I feed mine hamburger and steak all the time and they dearly love it. It was a treat that you gave her that she loved and actually ate.
If she had the sneezes, she had some type of respiratory illness and just couldnt shake it. Not sure what she had, but you gave her comfort in her last moments. Had nothing whatsoever to do with giving her the steak so rest assured about that, it probably helped make her feel better even. When any of mine are sick I will give them anything they want in order to get any food in them, so you did right there.
Hugs to you, she sounds much loved. So sorry bout your lil love passing.