Why Should I Trust Again?

I concluded a conversation not long ago with a young man who is currently attending college that really sparked my thought tank. He was in a relationship with a young lady who he'd met there last semester. He feels as though the amount of time, effort and affection that he had invested in the relationship was not honored by this young lady. He says the young lady wants to continue in the relationship but she had been hurt in her past from several relationships. She asked him this question: Why should I trust someone again? The young man says that if could come up with an intelligent enough answer she may be willing to ration some of her trust to him. I am not an expert but many people think that I am because I learned how to be a good listener. I hope the experts or the over comers of this barrier will pour in some advice to this post. Thanks and God bless