It sounds to me like your daughter is dealing with a dairy allergy. That is far from normal to be suffering from congestion that long. You can read about dairy allergy if you click on the button on the left "Allergy Wisdom".
In the meantime you can try fennel tea with some lemon and honey. Make sure you don't use raw honey otherwise this would be very safe for your 2 year old. You can read about fennel tea and get some recipes if you click on the button "Medicinal Teas" and just scroll to the middle of the page and find the link for Fennel Tea.