"Mais ou sont les neiges d'antan" means "where are the snows of yesteryear?" - basically, she's saying how fast time flies.
Those words come from a poem by François Villon where the poet expresses how the time fles.
That was from the 2011 Christmas Special (series 2), the meaning is covered in the notes section. Is that the one that was intended, or does she use another phrase in series 4?
What do you think?