Hi, Thanks for using HCM.
As she has taken emergency pill, chances of pregnancy
are less, and 21st day of cycle is a safer period, need not have to worry.
White discharge after sex could be a vaginal secretions which is normal during intercourse.
Frequent use of emergency pill is not advised.
Hope I answered your question. Consult your doctor for further examination and management.
Feel free to ask me if you have any further queries.
Wish you good health. Take care.