In a large saucepan, bring 5 cups water and the evaporated milk to a boil. Lower the heat to medium-low, stir in the grits, partially cover and simmer, stirring, until just thickened, about 15 minutes. Remove from the heat, stir in the cheese and three-quarters of the scallion greens, season with salt and pepper and cover to keep warm.
While the grits are cooking, in a large skillet, cook the bacon over medium-high heat until almost crisp, about 8 minutes. Season the shrimp with salt and pepper and stir into the pan along with the scallion whites; cook until the shrimp is opaque, about 3 minutes. Transfer the shrimp mixture to a bowl; wipe out the skillet.
In the same skillet, heat the olive oil over high heat. Season the okra with salt and pepper and toss with the flour. Fry the okra in a single layer, stirring occasionally, until golden in spots, about 3 minutes; drain on paper towels and season with salt.
Divide the grits among 4 bowls and top with the shrimp mixture and okra. Sprinkle the remaining scallion greens on top.