This may be due to a stone or blockage in her Salivary gland. Swelling below the ear and behind the jawbone soon after eating indicates blocked tubes in paroid slivary gland. Since you live in a remote area and want a temporary remporary relief - try cold compressions with Ice packs.
Next Steps
Visit your local pharmacy and take a painkiller and antibiotic as advised by the pharmacist as a temporary measure. Drink plenty of water.
Health Tips
Visit a ENT doctor at the earliest for correct assessment and treatment.