I'm not a doctor, but
If food was getting stagnant, I'd think there would be an odor even if the person brushes their teeth and washes their mouth, is there?
slightly it is there. Some gradual obstruction is there in the food pipe. Not sure if it's inflammation or anything serious ! :/
There are many things that could be causing those symptoms, but the most common would be a condition called achalasia. With achalasia, however, it tends to have a more insidious onset (over a longer amount of time), instead of just in the past couple days. Perhaps you could ask her if she had problems similar to this in the past, or if she ever has trouble choking on solid food.
Here is some info on achalasia :
When you swallow food, the esophagus has to squeeze the food on down to get it to the stomach (like squeezing toothpaste from a tube) (peristalsis). When it gets to the area that the stomach and esophagus meet (the gastroesophageal junction [GEJ]), a muscle there must relax for the food to be transferred from the esophagus to the stomach (the lower esophageal sphincter [LES]). The purpose of the lower esophageal sphincter is to keep the stomach contents closed off to the esophagus when we are not swallowing, so that food and stomach acid cannot just slide back up the esophagus (otherwise, if you stood upside-down, all of your stomach contents would come out of your mouth).
Achalasia can occur when that lower esophageal sphincter refuses to relax and let the food through. When this happens, the food stays stuck in the esophagus.
There are studies that can be done to diagnose achalasia, the two most common being esophageal manomentry and Barium swallow. In esophageal manomentry, they measure the pressure of that LES in response to swallowing. In Barium swallow, they take a series of x-rays of the patient swallowing something containing Barium, to visualize the contents going down the esophagus.
The most common treatments for achalasia are: 1) medical (take a medicine, like a calcium-channel blocker or nitrates) that will relax that LES, or 2) pneumatic dilation - where the doctor sticks a balloon at the GEJ, and inflates the balloon, so that it ruptures the muscle fibers. Lay-people usually refer to this as "having their throat stretched."
Again, there could be many other causes, but this is the most common.