You have no choice

Lanni let out a breath as she looked back at Lin Jian who was seriously waiting for an answer. "None that should be your concern." She finally answered emotionlessly. 

She knew that Lin Jian was only looking out for Xiehan and was afraid that his friend might be betrayed. Despite this, she didn't think she and Lin Jian were close enough to discuss such personal matters. How could she tell Lin Jian who Flynn was? If she did, she would also have to explain why she was in contact with such a person—then she would have to disclose her past altogether. 

As expected, Lin Jian was dissatisfied with her dismissive answer. He frowned and gave her a warning glare. "I don't personally care who that guy is nor why he seems to be close to you but I'm warning you. If you do anything to break Xiehan's heart…" 

Xiehan sent him a chilling glare and he shut up, mumbling to himself, 'I'm only looking out for you, Geez!' What an ungrateful friend!