I am a mother of soon to be four. My second child, a son, has suffered from croup ever since he was born. Every time he gets a cold it always turns into croup. He is now seven years old so we have been dealing with this for quite some time.
I am currently working toward becoming a Master Herbalist so the advice I have to give is completely wholesome, non-toxic, no chemicals involved and is safe for all ages. The first thing you want to do is stay calm for the sake of your daughter. Then turn your oven on to 250, cut an onion in half, and bake it uncovered in a glass oven dish for about 1 hour. While this is baking, stand with your daughter in front of freezer, or wrap her in a blanket and take her outside, in order to breath the cool, dry air. This will help reduce the initial swelling. When she has started breathing better make some peppermint tea by boiling some water, place some cut, dry pepper mint leaves into a tea ball and put that into a mug. (You can buy the peppermint at a health food store and a tea ball you can usually get at any grocery store or health food store.) When the water is boiling pour it into the mug and allow to sit for about 10 minutes (you can add a small amount of honey to sweeten). Let her sip at this while the onion is cooking. Peppermint helps to relax the muscles, especially in the esophageal area.
After about an hour pull the onion out of the oven and cut it into large pieces. They should feel somewhat slimey to the touch. Rub some olive oil onto your daughter's chest and then place the pieces of onion directly on her chest (blow on them so that they are not so hot that they burn her). Cover that with a wash cloth or small towel and hold it in place with a tight shirt or bandage. If you use a bandage make sure you do not tighten it so much that she has trouble breathing, but tight enough to hold the onion in place. Let her run around if she wants to or if she wants to sleep have her sleep in a semi-reclined position.
I leave the onion on for anywhere from 1 hour to 3 or 4 hours depending on how active my son is. I do notice that he is able to breath normally within 20-30 minutes after applying the onion. I repeat the process as often as he needs me to but his coup never lasts for more that 2-3 days with this regime. Whereas before it would last for 1-2 weeks.
I would also recommend that she stay away from foods made with animal products, especially dairy, while she is sick. Feed her fresh fruits and vegetables during this time. I have found that, for us, this has been the best and fastest way of healing each time we deal with croup. I hope that you are willing to try this and that you get good results as we have.