yup.
First ask her why she is afraid of dogs? Ask her for specifics. Start with the worst first.
Did she get bitten?
Did she get barked at?
Did she just hear from someone else - like a child at school about a bad situation or a bias?
Ask if she is afraid of other animals? Especially mammals.
Get a book on mammals and go through it with her and talk about the positives of the animals in the book, then get a good book on dogs, emphasis should be on positive traits - you can probably find one in the library. Eyewitness books are good.
Teach her that dogs are man made and we bred then to do different things. I would pick big breeds like the Saint Bernard and Leonberger to talk about since they are the least assertive dogs in the whole lot.
You can find stories on line about dogs saving people like in Joplin recently and there was a story I will never forget - true story.
There was a woman who lived in northern Los Angeles and she adopted a Rottweiler puppy, the tiny puppy seemed aloof and was not interested in being held or petted until one day the woman desperate to bond with the pup made some little whining noises, the pup responded and since then thy have been very close.
This woman would walk her dog, which of course grew by leap and bounds daily, around the block every morning, afternoon and evening and every day they would see a woman and her little girl. The mom would always pull the little girl away saying how viscious and mean "those dogs are" and how the little girl should stay away from dogs - they are no good, they smell, they roll in things, they shed and bite and get into garbage....on and on everyday.
When during an earthquake, the rottweiler ran out the door, jumped a fence, ran down the block and into a house. In that home was the little girl, she was standing in the middle of the kitchen. The dog went up to her and pushed her against the kitchen cupboards saving her from being hit on the head by a microwave which was on top ot the refrigerator. The dog changed all those days of her mothers bias against dogs.
There are thousands of stories like this which happen everyday. Once your granddaughter starts to welcome the information on dogs ask a local rescue or pound if someone can bring a big dog out for her to walk with. Dont have her touch the dog just go for a walk with it. She need not even hold the leash. Little by little you can help her understand what marvelous creatures they are and how they need us as much as we need them. Good luck, let us know how it goes.

I guess I am of the opinion that a fear of large dogs might be a healthy response in a six year old and not so sure I'd be encouraging a child to entirely lose it. I see too many parents letting their small children approach strange dogs, even when the dog owners are attempting to warn them not to. I know it happened a lot with my last dog, a schnauzer.

I guess I am saying that an adult must use a lot of discretion in dealing with animal fears in children. You may want the child not to be afraid of a specific dog, but they need to know that other dogs may not respond like a family pet.

I know what you mean Calliope. We rescued one of our dogs out of a bad and abusive situation. She was very fearful of everyone at first and would snap at strangers if they put out their hand too quickly to pet her. Parents seldom tried to stop their kids from assuming it was ok to approach a strange dog. It was very frustrating.
As to the op, I think it's a good thing for a child to have a healthy respect for dogs they're not acquainted with, but not terrified. Mazer gave some good advice. Also if you could find situations where YOU are petting and socializing with a big dog who is known to be very easy going and friendly, and let your granddaughter just watch you. She'll eventually get over it. Good luck

The child is terrified, not tentative or respectful.

Parents often unknowingly reinforce their children's fear by assuring them and feeding into the fear. Much like how people reinforce their fearful dogs.

So when I have a class with a fearful child (I teach Humane Education), I ask the parent if I may separate her from the child and basically include the child in the class ignoring the fear. If the child does not want to pet the dog, I ask her to sit with me while the other children interact with the dog. I would say 8 times out of 10 the child asks to pet the dog when the other kids are done.

I have other methods, of course, since everyone is different.

The upshot is this:

Don't reinforce the fear; be respectful but ignore it.

Have the child meet the dog in a large place (as opposed to a living room)

Have other children there who are not fearful.

Mom, do not encourage the child to sit with you and assure her safety. This reinforces fear.

Also: I teach classes on Dog and Cat Safety, which include lots of slides of dog body language and child role-playing. Learning about unsafe situations, dog body language and "reading" dogs' minds empowers the child with knowledge.

The more you learn about a subject, the less you fear.

It is a very successful class, the most popular one I teach. I think that class helps fearful children more than anything else. I have parents come to me and tell me their child would never pet a dog before, and can she take a picture of her with the dog!

So look to local animal welfare centers for classes on safety.

I see no reason why this is a problem. The dog is bigger than her at least as she sees it and she is not about to meet a big bad wolf. No big deal. As she gets older she may feel different but for now " No way". I wouldn't want to be dragged up to an elephant and told he wasn't going to hurt me. Forget it. You pet it and leave me out of it. JMHO

Children(and adults) often fear what they do not understand.

Your granddaughter needs to learn how dogs act, how dogs actions signal what the dog is going to do, and how she can learn to control most properly trained dogs.

One way to accomplish that would be to get her in a program where she can see/help train dogs. The more she learns about how to work with dogs, the less she will fear them.