Could be...but remember she already knew he was 'Don' and 'Godfather' the moment his father died. She knew the business he was in, that his family had always been in, and apparently married him based on the promise that business would one day be legitimate. Yet even Kay knew it couldn't happen overnight. They hadn't even moved to Vegas yet, but were packing. There's nothing to say (unless it's in the novel) she knew anything about 'the others', since prior to Connie's outburst Kay probably did follow respect Michael's wishes that she keep out of his business.

So I can't really go along with the theory that seeing a bunch of guys line up to kiss his ring would suddenly prove a revelation to Kay that her husband was indeed a murderer, and especially the murderer of his sister's husband.

Not that it isn't a reasonably interesting guess...

Apple