The reasons are most often hormonal - thyroid gland at the first place can be reason or imbalance of sexual hormones.
Stress is also possible reason.
Lack of certain minerals ! is also possible reason, but usually all these reasons exist at the same time.
She needs to calm down, check her hormones, balance them on some natural way, replace missing minerals and regularly massage her scalp - 2-3 times per day (ricinus oil is good for massage, or even pure 70% alcohol).
She will not loose her hair, if she starts acting now, hair will grow again, she does not need the surgery. Actually hair transplantation usually does not help if above mentioned conditions are not OK (hormones, minerals, circulation of scalp),because in that case transplanted hair falls down in few months. It is better to start with massage today and with minerals and balancing of hormones -soon. Everything will be fine.