In the visitation convent she entered, she was of good example to everyone because of her charity and humility. Often she made others impatient since she was rather slow and clumsy, but she was dear to Jesus, and He began to appear to Sister Margaret Mary to show her to spread devotion to His Sacred Heart. It was a very hard thing to do, because people thought the good Sister really had not seen Our Lord at all. Some were very angry with her for trying to spread the new devotion, and all this brought great suffering to the Saint. Yet she still did her best to carry out Our Lord's wish, and today, this wonderful devotion to the Sacred Heart is practiced all over the world.
Our Lord made a great promise to St. Margaret Mary for those who are devoted to His Most Sacred Heart. Some of these promises are; "I will comfort them in all there afflictions. I will establish peace in their homes. I will bestow abundant blessings on all their undertakings. I will bless every place where a picture of My Heart shall be exposed and honored."
Source; Saints for Young People for Every Day of the Year
A coloring picture of Saint Margaret Mary and the Sacred Heart can be found below.