I have no doubt that Comfortis is the most effective flea treatment for dogs. It kills fleas quickly, before the females can lay eggs and continue the life cycle.
Provided it is given with a meal, it will kill the fleas for a month regardles of regular bathing & swimming.
It is worth any extra cost to get a product which works well.
You have obviously spent time, money & effort to try & control fleas in your house as well as on your dog.
Make sure she can't get under your house or other shaded areas outside where fleas will breed.
Also, be aware that stray cats and dogs, wildlife & rodents can bring flea eggs into your yard.
Bedding should be washed in water hotter than 60 degrees Celsius to kill immature fleas.