Pregnant foster cat, just gave birth and is rejecting the kittens how can we get her to accept them?

My friend is fostering a cat, she just gave birth today and my friend told me the kittens were all tangled in ball. The umbilical cords were all tangled around them and my friend had to cut them all apart. She gave birth when my friend wasn't home and she came back to this situation, the mother cat cleaned the sacks off and the kittens were breathing and she says they are lively though she had to untangle and cut them all apart from the cords/placenta. But the mother isn't nursing or bonding with them. How can we encourage her? My friend has contacted the vet and she is calling the rescue. But any advice would be helpful.. to get the mother interested in the kittens and to get the kittens latching on.