Dr. Strange, thank you for sharing your find of the Lechmere funeral card. It's another piece of evidence to support the idea of Charles as a hard-working family man who raised his family and managed to leave some silver behind, too.
--------------- Von Konigswald: Jack the Ripper plays shuffleboard. -- Happy Birthday, Wanda June by Kurt Vonnegut, c.1970.
As I'm going to continue to "assume" This is the simplest and most logical explanation and it also comes from a professional in the field, unlike the second hand explanations and interpretations of others professional opinions that haunt this forum from time to time.
It has been intimated although not said outright that Liz consciously chose not to be buried with Charles because he was a killer. Since there is no concrete evidence (contemporary or otherwise) that Lechmere was a killer there is absolutely no reason to accept this is why she was buried where she was. They had several children and it may very well have been their decision where to bury her.
It is apparent that Miss Marple is correct. Pro-suspect people tend to make ambiguous statements and insinuations, such as the case here, and then when cornered by a question or request they tend to pull out the old standard "We'll never know" or "You can't be sure and shouldn't speculate", when this is what they're doing on other threads to boast their theory.
Hypocrisy is rampant and when you see it in writing, you realize how ridiculous people can be when they don't want to face facts.