Diastasis Recti can and does usually heal on its own over a postpartum period of 6 weeks to 3 months.
Within 6 weeks you should start seeing the Diastasis Recti go away slowly and then after 3 to 4 months the Diastasis Recti should be fully gone.
However it can sometimes last up to 6 months to a year before the Diastasis Recti goes away as it all depends on the person.
If it doesn't go away within 6 months then you might want to consider Diastasis Recti surgery if it's really bothering you and you have the money to pay for the Diastasis Recti surgery.
But if not then you could try a belly band to help with the Diastasis Recti which would be a cheaper option although the surgery for Diastasis Recti will fully get rid of it faster.