Slipped disks are extremely painful and not something to be messed with. You don't want permanent nerve damage. You did not mention exactly which disks it is.
I know it's a difficult process. I have a couple in my lower back. But seeing a doctor following MD orders which depending on the severity may include anything from physical therapy, to injections, to surgery.
But to help and give some relief for her pain icing it a few times a day for no more then 15 min will help. Heat does make it feel better but in ultimately will just hurt more but it can increase the inflammation.
I can't recommend any herbs that could help because she does needntinbe seen by an MD