Is it normal that my girlfriend has a tickle fettish?

My girlfriend gets really turned on by tickeling. She even has me do it while we have sex. Out of all the girls I've been with she's the only one that would get turned on by this, she even told me that I'm the only person she's told this to. I know there's tickle porn and stuff like that but has anyone else ever been with a girl that got turned on by tickeling?