According to Disney, when during the original films do the two DisneyToon sequels take place?
I suspect that in the case of Enchanted Christmas, their desire to do a Christmas movie completely steamrolled any worry of continuity issues.
But it really does open up the possible timeline of the film - it was temperate and pleasant when her time in the castle starts, and again when it ends. This implies that she was there right through the winter, starting in the fall and ending in the spring. So we're looking at anywhere between four to six months, including that winter.
So the answer to the question would be that Enchanted Christmas happens at some point during her stay at the Prince's domicile, if you adjust when that stay took place, and its length.
Wiki lists the events of Magical world as "after Christmas but before the fight with Gaston" so it would take place after Enchanted Christmas