Question Author
As a retired insurance company employee I know that to a motor insurer, a heart condition is a material fact, (in law, 'a fact that is known, or ought to be known by an insured, is material to be disclosed to insurers if it would affect their assessment of the risk').
What effect that might have on the terms of a policy or the premium is up to the insurance company but in the event of an accident in the UK, apart from statutory Road Traffic Act cover, it could result in cover being denied with serious consequences.
Her husband has already had an accident when joining a Freeway and I'm simply seeking someone with knowledge of American practice in order to be helpful.
barry1010's response is useful to know.
If you read my question properly, bednobs, you will see that she did not say she was frail and I'm not seeking to tell her not to drive, simply wanting for her to know what the law is in her country as I suspect she is ignorant of some of it.