welcome to hcm,
I really appreciate your concern,
Are lymph nodes painful?
Swollen ,tender,painful lymph nodes are indicative for infection.It might be an viral or bacterial infection.
Common causes are :
Strep throat,
Mononucleosis,
tonsillitis,mouth sores etc.
If not then it can be a cancer for that you need to undergo a test called fine needle aspiration cytology.
Usually an bacterial infection needs a course of antibiotics such as bactrim which you took, and an viral infection doesn't require specific treatment.
To improve her symptoms she need to rest ,drink plenty of water,eating healthy.
-applying a warm, wet compress to the affected area may help.
-She can take NSAIDs to reduce the pain and inflammation like: Ibuprofen ,
Acetaminophen .
If she start to have fever ,or the symptoms doesn't seem to improve,she need to consult a physician and get examined.
A detailed medical history ,physical examination ,
Complete blood count test are necessary for the diagnosis.
Please let me know if you have any questions,
thanks.regards.