Watch her ears closely, she is at the age and risk of ear infections with all that fluid.
Not to scare you, but do not treat this lightly. At this age allergies left untreated can become serious. With a high risk of developing asthma, ear infections, illnesses and more allergies (due to an already weakened and taxed immune system)- our son actually got a nasty sinus infection while we were tyring to figure it out, it was so frustrating! Go see an allergist. We love ours and so does our son.
If it's clear its allergies- it sounds likes allergies to me- my son started with his allergies when he was 1 and we kept thinking it was a cold, it wasn't until we started treating it like allergies that it helped. He is 3 now. The humidifier didn't help during the spring time (when it's at it's worst). We have tried a variety of medicines and find that a nasal spray with Allegra works the best, without making him sleepy. I would stay away from Benedryll and Dimeatapp, but that's me. Anything that makes them overly sleepy at this age is not a good thing. He takes his medicine easily, sometimes we "give" it to his stuffed animals first!
His are bad so we really changed our home & life to try to lower his risk of asthma. We gave away our two dogs :( we replaced the carpet and fabric furniture that the dogs were always on and we rarely open our windows- using the air conditioner instead. And we stopped swim lessons after I heard that exposure to public pools increased a risk of later asthma (they thought it was the high level of chlorine with developing lungs). I can honestly say he is so much better than he used to be. Still not great this time of year, but I was at me wits end last year always seeing him with bags under his eyes and "sick". By the way- The first time we got a real christmas tree he was a mess!!! From now on we will get a fake one.