Umm, well it depends on diet, type of hognose, if she brumated, etc.
Most hognoese by the time they are 1 year can be around 6 to 12 inches long, depending on how much they feed. By two years they are pretty much full grown but kinnda skinny and then rapidly put on weight as they reach sexual maturity. It's different for evey snake just like it is for people.
General rule of thumb is by around 2 years they are fully grown.