Well, it's read. Interesting. Obviously a crime of passion and thus, she was incredibly lucky to have done it without a lot of expressions of that passion beforehand. If she had expressed her anger...and had waited for him to actually say what he had done or was doing...the neighbors would have heard and that would have made the police more suspicious. In fact, that she did it before he said what it was he had done/was doing, makes the whole story suspicious. Reactions to bad news usually take the form of shock...led by denial. Thus, when he begins to tell her, she is shocked, but the first thing she does is act, not deny. In other words, her reaction is out of sync.
The same goes for her reaction to the whole thing. No where do we find her asking why? Why did somebody do this? doesn't seem to be on her mind. That too, would be noticed. But of course, she already knew why, didn't she? And that sets her reactions more out of sync.
That the cops knew her but didn't suspect would be, at first, reasonable. But certainly they would have noticed she wasn't reacting to her husband's violent death the way a woman usually would.
Overall the evidence would convict her eventually. That they ate the evidence wouldn't make much difference because they could easily reconstruct the weight and size of the leg of lamb from the bones and amount of time it took to cook from being frozen. If they knew, as suggested, their was some hanky-panky going on, that would give them a reason to suspect her. And finally, since the murder victim was probably involved in some kind of relationship, the woman (I assume) would be questioned even if the man's wife was not a suspect, and she would have revealed, in all probability, that the man was about to tell his wife, "it's over." Means, motive, opportunity, in this case, are easily ferreted out and the culprit would have been found out, giggles or not.
AJ