Just saw this scene, the movie can be watched for free on tubi tv. It's the main gorgeous actress Ashley Laurence from the first 2 movies that gets tickled also and her laughter is so girly and adorable. The guy tickles her upper body with one hand while he's driving the vehicle with the other so I'm guess she doesn't tickle him back because she doesn't want him to wreck so she just takes it while laughing uncontrollably and begs him to stop. Great scene.