Cousin said there was no one behind me. What is her motive?

According to the information you gave, it is difficult to determine your cousin's specific meaning or intention. The sentence "there is no one behind" may be aimed at some people or situations you said. She feels that there is no support around you or what she said is unrealistic. It may also be an easy joke that I accidentally said. Therefore, the best way is to ask her directly and listen to her explain the specific meaning and intention of this sentence. This can avoid misunderstanding and speculation, and better understand each other's thoughts and communication.