Hi, Sorry this is long!
I'm having the same problem with my six year old. Our problem started when I realized that he was having a problem with attention and behavior in his classes at church.
I started observing him and found that he wasn't listening and would get up and walk off and kind of mean but also loving. I looked at a book that I saw on Dr. Phil by Dr. Frank Lawlis, The ADD Answer. I thought that he had ADD from his behavior. Anyway there was a section on sleep problems and most match my son. I just thought he was going to be a snorer. In short, we went to ENT and found that he had 3+ tonsils (4 is touching), had a sleep study done and found that he has mild to moderate sleep apnea. He stopped breathing 30 times during the night and for 26 sec the longest. I say that because when I observed his sleep I only thought he stopped for about 4-5 sec. Big difference.
The same day as his sleep study, we had him allergy tested and found that he was allergic to dust mites, and some other things. We did this because he was also swollen up his nose and seemed to keep a stopped up nose.
I wish we had done the allergy test and got him started on the meds before doing the sleep study, because the results may have been different.
I don't like giving my son the meds, but having sleep apnea is worse. He has never had problems with ear infections or strep throats. He started snoring about two when we lived in a moldy home. I have cut out dairy but that doesn't seem to do much for the nose but for the attention.
The guy doing the sleep study told me that alot of kids are on Ritalin for ADHD and all they have is sleep apnea.
The doctors want to remove his tonsils and adenoids. I have been at odds because of the lymph issue and of course they say that there is enough lymph in the head. Well, I had my tonsils out when I was about nine and I am the sickest one and fattest one in my family. I asked the doctor about a unilateral removal of the largest tonsil and leave the other one. She won't do that.
So I asked her to xray the adenoids to see if they were big. Why remove them if you don't know for sure that they are big. I mean he hasn't had any problem with ear infections. She came back with they are big also. So I think I'm going to take him to another doctor and see about removing only the adenoids or just one tonsil.
Some posts I made about my son... These got a response.
The Halleluiah Diet was suggested and might work. Your daughter seems to be healthy and a healthy eater, my son isn't. She might actually do the Halleluiah Diet. You know drink that green stuff.
My son has always spoke clearly. My other child is like you daughter. He is 3 1/2 and I can only understand about 1/2 of what he says. And, his language evaluation shows him delayed in speech reception and expression. I guess so I can hardly carry a conversation with him. It makes me sad to hear him talking and saying the same thing over and over again and I can't understand him to give him an appropriate reponse. Have her check by your local school speech and language pathologist. It's free.