Q - Can diet encourage age of laying?
A - Yes, If you are feeding a incomplete feed and or offering a lot of treats.
 
Q - Is this because of her age or breed or am I not feeding her correctly?
A - It could be her age and the breed if you got her from a good breeder that breeds show quality birds, exhibition fowl tend to take a little longer to mature. 
 
Q - I read that increasing protein at this age could get her to lay.
A - If you are feeding a low protein diet (less than 15% protein) then increasing the protein may encourage her to lay. Hen will lay well on a feed that is as low as 16% as long as they are not fed treats.
 
 
What type of feed are you feeding your hen, what is the protein amount, does it contain animal proteins, and do you offer lots of treats?
 
Chris