The superficial meaning of this sentence is that if this boy finds true happiness, whether alone with her or in other ways, she will feel satisfied and think that this is the end or conclusion of their relationship. This shows her love and concern for the boy, and I hope he can be happy.
However, the true meaning of this sentence may vary according to the context and the mood of girls. If the girl is sincere when she says this sentence, she may be expressing her love for him, hoping that he can find true happiness. If a girl says this when she is angry or disappointed, she may be implying that the boy's behavior or attitude makes her feel unhappy, so she thinks this is the end of their relationship.
Therefore, according to the information you provided, it is difficult to accurately interpret the true meaning of this sentence. You can consider communicating directly with a girl to find out what she really thinks.