My client has had 2 caesarians. With cardio, core training, good nutrition- how much ab tightness can she get back?

My client has 2 kids, the youngest is 4 and both delivered through caesarians. She has lost most of her baby weight, and we include lots of core training in her routines. Any suggestions on what else we can do and how realistic is it for her to expect her abs to return to pre-pregnancy firness/strength? How much more difficult is it to lose this baby fat than with vaginal deliveries?