Short form: If it involved macaroni and my mother and was not a glue-art-project, you should just run away. Mostly with mac-and-cheese she consistently did something that caused the dairy products to seize so it had that weird gritty texture. Now, I have done this and eaten it anyway because, well, sometimes things go awry. But I've done it once or twice...

Also overcooking. And bad combos. and so on.