I'm not a ladie but,
With our DD we had a very similar (although not as drematic) circumstances.
We tried every cold / blocked nose remidy going new and old to no use. We eventually came to the end of our ropes and said we had to try something else as the amount of saliva that was coming out of her mouth was not normal.
We had her adnoids & tonsils removed to help free up some space as the doc's thought that was the issue
We thought we would try non-dairy substitute for her milk, yougut etc. This has workd wonders
Who would of thought that all of the blocked stuffy noses where a reaction to Lactose or cows milk.
Now we have to be very diligent wherever she goes to assure she is not getting given cows milk, as you can tell straight away the next day.
We also tried to have DD sitting up (not far just not flat) and that seemed to help. But what you might want to consider is getting a thickener for the milk to stop the youngster from knocking down to quick.
Hope some of this helps as I know what (or some of what) you are going through
Take Care & best of luck.