She sang on the songs `` I 've Got a Theory \/ Bunnies \/ If We 're Together '' , `` Under Your Spell '' ( her solo ) , `` Walk Through the Fire '' , `` Standing\/Under Your Spell ( Reprise ) '' and `` Where Do We Go From Here ? '' She provided vocals for the songs `` I 've Got a Theory \/ Bunnies \/ If We 're Together '' , `` Under Your Spell '' ( her solo ) , `` Walk Through the Fire '' , `` Standing\/Under Your Spell ( Reprise ) '' and `` Where Do We Go from Here ? ''