Yes short answer. I hope your wife is doing much better.
It is shared cost. AETNA is denying because Medicare ALWAYS pays first then AETNA. Call the hospital and doctors offices and provide the the Medicare information. Problem should resolve.
I am retired VA Hospital Nurse and researched Medicare plans, my employer health plans and supplements for a year before I took Medicare. Employer plans pick up all remaining costs deductibles- hospitals, lab work, tests like mammograms, Xrays, therapy, etc, etc, follow-up copays including office appointments and pay whatever Medicare does not. What I found take Medicare A & B + KEEP employer plan you like and NOT buy supplement (duplication of benefits). Employer plan IS your supplement. Insurance and Medicare companies avoid telling you because they are in the making $$$ business. DO not need to take part C. Part D is prescription and employer plan likely covers your prescriptions already. If true, do not need Part D. When each of you have Open Season - can always change/tweak your choices.
For last 4 years I have paid out $0.00 medical however; prescription copays you pay (exception).
Also, think like you and wife are identified TOTALLY separate (like divorced). If wife worked should consider keep employer plan if likes it and NOT take straight Medicare only Part A & B. What you do need to think about if wife is on YOUR plan and you die first she will lose your health plan so need to think ahead. Hope this helps.
Medicare and AETNA will be stubborn since switching between insurance. Need to be diligent. Any questions or need help welcome to email me navymama72@hotmail.com