It speaks volumes that M wasn’t pictured at Balmoral with the Queen. It’s a private retreat for the Queen and she values her time spent there, therefore if Meghan was invited to spend time there it would actually mean something. When Carole was invited it had to have been because the Queen genuinely sought Carole’s company. The fact that M didn’t even get to attend church service at Balmoral pretty much means the Queen doesn’t care to be bothered with Meghan in less it’s in public.