I'm going to skip the circuitous illogic of Mary's response for a moment and offer my own good advice to Mary: Stop being such an arrogant busy body. Pride cometh before the fall, Mary. Pride cometh before the fall.
I really, really hope this is a set up for a new story where Mary ends up destroying someone's life because she's too busy to consider whether or not the advice she's giving is actually good. But alas, I worry it is simply denouement to the Vera and Drew storyline reminding us that even though she couldn't hook them up, she does have a "track record."