Zoloft and other medications in the same class can have an 'activating' effect with some people, but if that were the case you would see it at home as well as at school. So this 'hyper' appearance is likely not a reaction to the medication. It is very likely a manifestation of the anxiety she experiences in the social situation, and a reasonable intervention (in addition to therapy, preferaby group therapy) would be to try an increase in dose.