Lin Xiaolu was completely shocked by this revelation. Su Yanyan had a son and this was the reason why she was helping these bad people despite her own will. She was being forced and now Lin Xiaolu understood why Long Xun decided to marry her even after knowing that she was against him. He must be knowing about it and that why he was so happy. That's what he meant when he said that Su Yanyan was not what she looked like.
After knowing why Su Yanyan was helping these people, Lin Xiaolu was so much angry at these people. Long Xun had told her how these people worked. To make Su Yanyan work for them, they used her son just like how they used Long Xun's mother to make Long Xun's father work for them. After knowing the truth behind that incident due to which she got separated from her parents, she wasn't angry. Long Xun had apologized to her a lot and she forgave him and his father because it wasn't their fault. She understood their reason, their helplessness.