Why does Mrs. Levi try to convince Ambrose to get Mr. Vandergelder's blessing in the play, The Matchmaker?

Mrs. Levi recognizes that if Ambrose and Ermengarde marry without Mr. Vandergelder's support, they will live a life filled with poverty. As Mrs. Levi is poor herself, she knows this life is not the ideal climate for young lovers, especially when there is still hope for them to have some means for a better life.