Its not likely that she is having an infection. This may sometimes accompany pre menstrually i.e. before periods. She may be having a subclinical infection.
Next Steps
Plenty of water to drink (at least 3.5 litres per day)
Be watchful to follow her symptoms.
Repeat Urine R.E. & Culture if symptoms persist beyond 7 days.
No marital relations for the time being.
Health Tips
Don't worry. Be positive she will recover soon.