Katies Website opend in 1999. That does not mean she was legal and 18 at that time. She did not have any nudes that i can find until 2003. So like other web models she could have posed for NN pictures prior to the age of 18. Altough,there is a rumor that her BF let out nudes he took of her at 16 to 17 years old. cant confirm that and have never stumbled on anything like that before. Famousboards has a comment stating that katie was 28 in 2011. So it looks like Katie is 31 to 32now. That is not for verified 100% for sure but a very educated guess id say.
Earliest year stamped pic i've found: Year 2000, i could not find any year stamped 1999:
Earliest year of full nude i've found:
Earliest implied nude i've found: