Up front, I think ABC should've declined the fight and Dern should be forced to 125 for at least one fight. But I honestly think the weight miss was intentional, calculated and damned effective (especially since fighters can't re hydrate with IV fluids).
You just don't miss by that much. That isn't a miss, that's a plan. Dern was able to fully recover from camp, experienced no diet gyrations, no weight cut dehydration and was able to collect 70% of her purse for fighting someone a full weight class below her who had gone through the cutting process. She's catching some shit for the miss, but she's also catching just as much praise for her victory.
I know this isn't exactly Dick Fucking Tracy, but my point is she played the rules, or more specifically their laxness, to her advantage. The rules need to change. The UFC needs to impose tougher restrictions. Maybe s/he should forfeit 75% of their purse and be forced to compete in one fight at a heavier class before being allowed to cut back to their previous weight class? I don't know, but the org needs to take decisive action.