I think it is the effect of post partum for your wife. This could be handled by good attention to her,  proper rest and care by an extended support from either one of ur families.

Post partum period is a vulnerable time for the new mother due to the hormonal changes in the body after delivery. In such situations it is common for them to develop depression or any behavioral changes. Symptoms can vary from lack of self care, lack of affection towards baby, not taking care of the baby, suspiciousness, odd behavior, and can even lead to her harming herself or the baby. It is essential you get a consultation immediately from a Psychiatrist for her before the situation deteriorates. Get a home visit if she is not able to travel. In the meanwhile please ensure that she is never alone with the baby. Keep supervision on her. Also as this is an overwhelming time for her, give her as much support and help as possible. Help her take care of the baby and herself, and ensure she is eating and sleeping properly.

Since apart from depression, she also is suspicious & talks to herself, she may be suffering from post partum psychosis, which can happen in a few mothers post delivery. You need to immediately consult a psychiatrist. Till she becomes alright, some family member has to take over the responsibility of the newborn & supervise her while she is with the baby.