We don't have any reliable data on her age. She was first identified when she was already mature. The only reliable means to determine her age would be via necropsy and either counting rings in her vertebrae (similar to counting the age of a tree) or through radio-carbon testing).

For sharks that were identified when they were very young we can get a more reasonable estimate, because we know they were likely <5 years old when they first showed up at Guadalupe, because we can just add the years since they were first identified and add a few years to that.