Cats register the presence of food by smell; when food is refrigerated, it has far less scent than when it's fresh from the (room temperature) can, and for many cats, the comparative lack of scent from refrigerated canned food will make it unappealing.
You have the right idea that the (lack of) scent is the issue, but not on how to bring it back. While it's important to keep the food covered to retain the moisture, temperature is the real key to solving the issue. Before serving the food, microwave it lightly in bursts of just a couple of seconds to warm it back up. You don't want it hot, only around room temperature to lukewarm--roughly the temperature of freshly caught prey. Take it slow and give it time after removing it from the microwave to make sure it's not overheated.
You might also try transferring the food to a different container, if warming alone isn't sufficient. Depending on how picky your cat is, the food could be picking up a metallic odor from the can during the time in the fridge that she dislikes. I personally use a plastic container for my cats' food, but you can use a glass one, too, as long as it has an air-tight seal. If you're still having trouble, consider a "stinkier" food that will retain more smell when refrigerated, and thus when warmed back up.