If Chen Jun were to get remarried to Qiao Nan, the situation would be different. Based on her relationship with Chen Jun, Qiao Nan had always treated her son well, causing her son to throw tantrums, demanding to play with his younger auntie when he was younger. Qiao Nan would definitely treat her son well if she were to become his stepmother.
If Qiao Nan dared to do anything in this regard, the Qiao family would have their eyes on her. Chen Jun was getting more impressive by the day. No one in the Qiao family was an official, apart from Chen Jun. It would be a pity to sever all ties with Chen Jun. All these problems would be solved by Qiao Nan's marriage to Chen Jun.
In short, Chen Jun had a brilliant background. Instead of letting someone else take advantage of them and sacrificing her son's interests, she might as well be gracious and encourage Chen Jun to get back together with his ex, Qiao Nan.