To answer the question of whether the Lilac Fairy originally danced or not, one may look to the Kirov's reconstruction, in which the Lilac Fairy is in pointe shoes for the prologue (when she danced the entrée, adagio, variation, and coda with the other fairies) and heeled slippers and a gown for Acts I-III. So there is plenty of authentic material for her to dance, but (as far as I know) only in the prologue.