My hood has been pierced for almost two years now, and I love it. It does give a lot of added stimulation during sexual activity, but it doesn't keep you stimulated all the time to the point of causing wetness.

My guess would be that she was telling you this within the first few weeks of having the piercing done. If that was the case, then yes...once the initial discomfort has passed any type of contact will cause more stimuation than what you're used to, so you're naturally going to respond in kind. This passes once the piercing is completely healed and you have become accustomed to it.