It's almost impossible to tell unless you have raised her yourself. I checked out the original photos, and I tried to count the annual rings created on each individual scute. Now, I know that in some areas these scutes can be created twice yearly...in areas where there is a wet and cool spring, a very hot summer, and a wet and cool fall. They'll get a growth ring in the spring and then again in the fall. Based on size, this turtle could be a young adult or just a small adult. Three-toeds grow pretty fast. So, long boring story short, I think she's anywhere from 5 to 10 years old. I counted 9 or 10 growth rings.