Aunt Ning and uncle Jack came up with a plan. They decided to bring Lina close to Wang somehow, so that they end up getting married. This way, they would be able to get Wang to marry Lina within six months from now on.
For this plan to succeed, they needed as much support as possible. And getting Wang's dearest and most trustworthy friend, Smith, to their side was the first and the most important step in this plan.
They were going to try the old tried and tested technique of 'divide and rule'. Aunt Ning knew that Smith was pretty fond of Miss. Chunhua. And she knew that Chunhua wanted to marry Wang. Aunt Ning hated the thought of Chunhua becoming a part of their family.
So, Ning had a dual purpose for inviting Smith - Firstly, getting him joined in the plan of 'Wang's marriage'. Secondly, to prevent Chunhua from getting too close to Wang by making Smith feel insecure, and provoking him to fasten up his steps towards Chunhua.