Post-partum psychosis is a serious medical emergency and she will need to be treated by medical professionals as soon as possible. Treatment normally entails medical and psychiatric evaluations, possible medication, therapy, and support group involvement. Postpartum distress is a common result of the extraordinary process of pregnancy and birth. It is widely recognized that most women will experience some form of it following a birth. Overall, your best bet is to make sure you address her worries, reassure her that she's going to be a great mom and do everything you can to make life as easy and worry-free as possible.
Mutual support is the foundation for becoming great parents.