I'm not an expert. [Although I play one on TV] oops, sorry.
I have 2 theories. (I did do Infection Control for 7 years, and this was a "forever" discussion w/ the surgeons and the ID docs going at it ad infinitum and nauseum)
The 1st is that there is not very good circulation in adipose tissue, and that is not conducive to good wound healing.
the 2nd is that the surgeons don't handle that tissue very gently, i.e., leaning on it (with retractors), grabbing big clumps of tissue to tie off bleeders, or using a lot of cautery, which leaves a lot of dead tissue to be dealt with by the body along with the wound healing.
I'll bet it's a little bit of both. It sounds like it's healing ok now, and wet to dry NSS is a very gentle form of debridement. A WARM, not hot, heating pad for short periods of time (cover the wet dressing w/ Saran Wrap) might increase circulation to the area. I don't know if she's on a special diet, but see if you can make sure she gets enough vitamins, esp C, to help her heal.
A nice bouquet of flowers and a big kiss wouldn't hurt! Best wishes, Ted.