Can you give us a photo of her facing forward? Are the wattles swollen too or is it just limited to one side of the face (are both sides swollen)?
Also, is there a main source of swelling - is there a peck mark, cut, injury that could have become infected and caused the swelling? Is she rasping, having trouble breathing, sneezing, etc.?
It's hard to know if the swelling is from respiratory illness or bacterial infection. Do you notice any discharge/mucous from the nostrils or eyes, does she have any swelling or plagues inside the beak?
If you have a vet that can see her to do some testing that would be best.
As suggested in the previous posts by @Eggcessive keep her hydrated. Add some poultry vitamins or electrolytes to her water. Her crop seems to be quite full looking or it could be the angle the photo was taken. What do you feed? Chick starter only - if she has had any type of foods other than chick starter provide her with some grit and monitor the crop to see if it is emptying over the course of the day.
Keep us posted.