When you visit your doctor, ask for allergy tests to be ordered for your daughter or a referral to an allergist. You need to find out the cause of the congestion so you can eradicate it instead of just trying to treat the symptoms. I've suffered from allergies my whole life and my mother took me to get a skin patch test when I was very young. Turns out I'm pretty much allergic to all life on this planet. Sucks to be me!
Maybe you'll find out your daughter is allergic to a particular animal or plant she's coming into contact with and you can remove the allergen from your home.
It gets better though. I was a miserable snot nosed little booger factory growing up but now I have two cats, a bird and even some indoor plants and no congestion! Some allergies just get outgrown I guess.
Another thing that helped a ton when I was all stuffed up and miserable as a kid is a humidifier with a reservoir for some vicks vapo liquid. Set it up to run at night but make sure to air the room out during the day and wipe down the window sills so you don't get mold growing there.