A cat can be on a quality dry food, wet food, or both. In a young cat there is usually no medical reason they should have one over the other.
Wet food is nice in older dehydrated cats because it contains much higher moisture content. It can be easier to manage weight on a wet food diet, because they are generally less calorie dense than the dry food.
Dry food is nice because it helps prevent tartar buildup, and is generally better for your cat's dental health. Dry food also tends to be a bit more filling, and contain more carbohydrates.
Nutritionally, dry foods can be just as healthy as wet foods. Obviously, there are 'junk foods' out in the cat food world just as there are in the humans world, so do some research into the brand you choose.
It is fine to free-feed a cat dry food as long as they can regulate their intake. Most cats are 'naturally' grazers, but some cats have less self-control than others. She is young and active at the moment, so may be able to maintain a healthy weight. But as she gets older, watch to make sure she does not get overweight. If that happens, you may need to start measuring out the dry food.
As in most things in life, it's about finding a balance. And finding a food that your cat enjoys to eat.