"I invited her here to be my bride's bridesmaid. Isn't it wonderful, Chen?" Mo Lingtan asked cunningly.
Lu Yichen had a strong urge to kill Mo Lingtan right that instant, on his wedding day itself. However, he tried to control himself, not because of Lee Xuiye instead, but for himself and for Jenny.
Knowing Jenny's nature, she would definitely feel that Lu Yichen killed Mo Lingtan because he still wanted to be with Lee Xuiye rather than with her. As a result, she would turn into a vicious person leaving her sweet nature behind.
In the end, he would lose his soon to be bride and be the party who would be on the losing end.
That was also a point of threat Mo Lingtan used to force Lu Yichen to be his best man. If he had not agreed, then Mo Lingtan would have stuck a fork in Lu Yichen and Jenny's relationship using Lee Xuiye's name.