The contact for Amhurst Cemetery is listed below, I am not sure that Betty is still doing it but if not she should be able to point you in the right direction. I am 99.9% sure that there is not headstone for your Dorcas as I only found her name int he burial register not in the headstone register.
Anja van Steel
Oct 14, 2009
Anja van Steel
Amherst Cemetery
Mrs Betty Fleming,
Secretary,
P.O. Box 53,
Talbot 3371
Phone: 030 5463 2397
Anja
Oct 14, 2009
Anja van Steel
Anja
Oct 15, 2009