Labrador dogs do not appear to be very tall, it is not a characteristic of the breed. Standard males reach a maximum of 56cm withers and females, like yours, reach 56cm. Her dog is still 9 months old and, unlike smaller dogs, contrary to what most think, they do not stop growing at 12 months of age. Puppies the size of Labradors can continue to grow until 18 months of age.
I can't guarantee you that your Labrador dog will reach 54cm withers, which would be the minimum allowed for the breed standard, the ideal would be for you to take her to a veterinarian for a complete and thorough evaluation. if necessary, it will start supplementation.