How long does open cat food stay good?

My cat needs special [expensive] canned cat food, like $1.50 per can. Shes very picky and will only eat it if its been sitting out for a while. It is a meat-based food. If I feed her the newly opened wet food around 7am, she wont touch it until about 3pm. A human obviously wouldnt want to eat plain meat thats been left out that long because it would be spoiled. My question is, is this harmful? Would she still eat it if it was bad/spoiled or would she know the difference? How long can wet cat food be left out at room temperature without being spoiled? Thanks!