Scammers, in some amazing way, tend to stay one step ahead of ethical people. I can think of several ways DeeDee may have influenced doctors or faked Gypsy's illnesses even if they weren't there:
1) Leukemia: She could've told the docs in MO G was diagnosed with it in LA and IF they did bloodwork, and she appeared fine, hallejuah! A miracle--G is in remission!
2) The doc(s) could be in on the frauds
3) The chromosome defect/possible MR--once that's diagnosed in infanthood, I'll bet no dr. ever did tests to confirm it later. They prob took Dee Dee's word for it. Think about it. If I go to an eye doctor, I fill out a med history form. He never tests me for the conditions I say I have...some dr's might, but many, if not in their area of expertise, just take the patient's word for it. And like the post quoted above, there are good, bad and indifferent doctors. I'll bet as a con artist, Dee Dee knew how to flesh out the ones that would be sympathetic to her ploys.
4) Of course, for chemo, oxygen, wheelchair, feeding tube, and other sundry needs, props could be easily faked and who is gonna call out a mamma on this stuff? And if any doc ever did call her out on it, voila! We're finding a diff doc! This one is a quack/doesn't care/or fill-in-the-blank. Oh, and people donated all the supplies, most likely, or Medicaid paid for them (if she could convince a doc they were necessary) so it's not like she had to fork out any of her hard-scammed dough for them.
Just a few thoughts on how the schemes could've been carried out...