I had a very young kitten, the runt of the litter, who got colic very badly when he ate too much for his very small self. He'd be in very obvious pain. Perhaps your kitten is having trouble digesting even the milk and has colic. In your place, I would push fluids over food at this point. She will dehydrate far faster than starve, and her digestive system may need a rest. I suggest tepid water via a syringe and continue the anal area massage. Hopefully, she will be at the vet's in a matter of hours. Good luck!