Get rid of the water quickly and that is the best solution to mildew, Shop vac and towels, $20 on a helms manual on how to remove the back seat and pull up the carpet with a fan on it. If you have a couple hours turn the car on, turn on the floor registers all the way and put the heat on full blast. Crack one window slightly. just a hair. Use leather conditioner on the leather so it doent get too hard.
Silica only pulls water from the air and barely can draw more than a few grams of water per ounce of silica. Better to put towels down and step on them to blot up the moisture.
You can also buy an electric heater with fan built in at wally world and put it in the car, careful where you aim it so it doesnt heat one spot excessively. Same as the cars heat, close it up and crack one window barely to warm the interior and evaporate the water
Good luck