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Delay the further procedures if you can and attempt to get her to try alternative treatment. As you already observed, clownworld doctors don't know what they are doing. TCM describes edema as a failure of either or both of the kidney (water metabolism) and spleen (controls blood/energy flow to limbs). When they are weakened, they start to slack off in their duties, and this is when you start to notice symptoms like edema. Conversely, once these organs are strengthened, they will catch up on the work they have to do, and the edema will go away.
Kidney and spleen problems tend to come with age and what our society considers as "normal" dietary choices. It can be caused from a lot of things, but again, it is not some giant mystery like the doctors you saw thing it is.
If you have the financial means, try to get her to see a TCM doctor. Acupuncture/moxibustion treatments will yield the quickest results, but they can be costlier. Herbal treatments are a cheaper and more sustainable treatment method. With either of these, however, you eventually need to treat the root cause, which is the lifestyle choices being made. This will likely be dietary changes, as well as the inclusion of exercise or yoga.
I recommend you skim this research article on acupuncture and edemaExternal ↗ if you remain unconvinced or skeptical. Additionally, do your own googling on the efficacy of TCM treatment for edema.
If the financial means are not present, then the easiest advice I could give is to just take the hatha yoga pdf, delete the 1st page that talks about Zevism, and send it to her and tell her to do it every day. If she is overweight, just take out the headstand/shoulderstands and whatever else she cannot do.
Diet wise, the simplest advice is simply: whole foods only. Eat 2x as many veggies as meat. Limit sugar, fried foods, and dairy.
There are certainly more advanced/more detailed changes that can be made, but these two changes would do a lot for her health. Enough so that you could quit worrying entirely. The yoga alone makes such a big difference that it is crazy.
Anyway, good luck. Again, this is not some mystery illness, rather it is just an imbalance brought upon by lifestyle.