Swollen neck glands - are actually inflamed lymph nodes.
This is the story in short and simplified words.Lymph contains high numbers of white blood cells(WBC) those protects our body from infections. Microbes causing infection are carried with lymph to the lymph nodes, engulfed by macrophage
(a type of WBC), and eliminated. If the microbes are strong (virulent / infective) enough, the battles goes on. Microbes multiply in numbers and body recruits more and more WBCs. If the body wins- infection is subsided, if the microbes win- infection progressed. Swollen lymph nodes
are symbol of inflammation in the node, i.e, the battle is going on.
Neck lymph nodes are drained from different areas of face, scalp, throat. So, exact position of swollen node suggest the affected area. It could be a blister
/ skin infection
on face /scalp, or in throat, or gum, eye etc.
If she has recurrent infection is in her throat (sore throat), get her examined by a ENT doctor. Enlarged adenoid
glands sometimes causes this type of problem. Another thing could be streptococcal sore throat
- be cautious, has problematic sequels. Or, simply this could be common cough and cold (Flu).
There could be different other reasons. I just mentioned the common fews.
Get her examined by a pediatrician
. Follow what he/she advises.