Here are a few words to ponder.
"The most infallible and indubitable sign to distinguish a heretic, a man of bad doctrine, a reprobate, from the predestined is that the heretic and the reprobate regard with indifference the Blessed Virgin Mary, and try by word and example to diminish her cult and the love of her, openly or tacitly , and sometimes with good pretexts. Alas. God the Father has not told Mary to make her dwelling with them because they are Esaus." (St. Louis de Montfort, True Devotion, n. 30.)