15 month old piranha

I called John today to tell him about my worries that CPS might call us concerned about the bite marks on Jack's arms - the bite marks left by none other than his little baby sister. It started off as once in awhile when she was pissed at him taking something. Ok, fine - you can't talk and you're frustrated...I get it. But - two days ago she got Jack twice within an hour timeframe, which clearly caused concern that this problem is becoming increasingly worse. Then yesterday as we're leaving the library, big girl wants to walk out to the parking lot herself; I go to pick her up, and what does she do? Yup - pulls out those fangs and goes for blood. I kneal down, tell her no (as we're in public, so I can't smack her in the mouth like I'd like), and immediately the woman behind me asks "Oooh...you going through the biting stage?" While I was embarassed by this eyewitness account, I was relieved to hear that this may just be a stage that will pass. In the meantime, she suggested next time it happens I should bite back. So...look out my sweet little piranha!