Interesting to hear she had a tongue tie.
Unfortunately, many mainstream HCPs are clueless about ties and the far reaching effects they can have on overall health. Sorry, but it's true. You say she had it snipped at a week old, however many ties are not completely released, sometimes an anterior tie can be snipped but a difficult to diagnose posterior tie may be completely overlooked.
The tongue shapes the palate in the womb and if the swallow pattern is restricted, it can leave distortions in palate shape which can in turn affect facial development. Not that you would notice unless you knew what you were looking for, but this is what happened to DS1.
Have a look at your DD's palate. If it is high and narrow, you may have your answer, or at least part of it. There are pictures on my profile of DS before he had his orthodontics done. The high narrow palate distorts and narrows the openings into the airway which can cause apnoea.
Interesting you say about the large tonsils. I thought DS had massive tonsils, but actually they were normal. They just looked massive because his tongue was tied down at the back and you could see his tonsils in their entirety without using a tongue depressor. After he had his revision, the back of the tongue now sits much higher up and you can't see his tonsils at all.
Is your dd a mouth breather?