The distinction between "can't do" and "can't get paid for" seems to get lost a lot with medical providers. I'm not saying this is necessarily what's happening with your wife, but I've had it happen to me where someone says, "I can't do this test. Your insurance won't pay for it," and then I ask what it costs and it's a few hundred or a couple thousand dollars and I say, "That's OK. I'll just pay for the test myself," and something short-circuits and they still can't understand that they can do it.
The most egregious example was a prescription I needed that my insurance wouldn't approve. It was $49 without insurance. But the pharmacy wouldn't sell it to me even though my doctor had prescribed it because they couldn't figure out how to take my money directly when I did have insurance.
I get that when insurance doesn't cover something, most patients won't opt to pay for it anyway, but it feels like we need more reminders on both the patient and the provider side that this doesn't mean it can't be done.