Thank you for the question! I'm sorry to hear of this unfortunate event following your DIEP flap. Acellular dermal matrices (e.g., AlloMax, AlloDerm, FlexHD, etc.) are collagen sheets derived from human cadaveric donors, which have been treated to remove antigenic cells and such. While they have revolutionized breast reconstruction in particular, they have been used to treated hernias and bulges for the abdominal wall.
It is quite uncommon to develop a true hernia following a DIEP flap, since the muscle should be kept intact and abdominal wall integrity changed very little if any. Bulges are more common, but much less than a muscle-sparing TRAM or the conventional TRAM flap, where the a portion or the entire muscle is harvested for the reconstruction of a breast. Regardless, these dermal matrices act as a scaffolding for tissue ingrowth and may be used for abdominal wall repair. The downside of these are the predictable stretch that occurs once placed. Although desirable for breast reconstruction in order to obtain better shape, it is not as ideal for the abdominal wall repair, as you ideally do not want any stretching following repair, but certainly could be used.
Your surgeon may consider a porcine dermal matrix which has much less stretch than the human type. If you are experiencing some bulging of the abdomen along with some discomfort, repair should be entertained and repair via tightening of the fascia alone or with the use of either human or porcine dermal matrix, or even a mesh, could be done. I hope that this helps! Best of luck with this!