She had to make a choice between her son's life and her own pride and independence as a woman. Once she gave in to this, then she had a feeling that she wouldn't be able to escape anymore.
Furthermore, the young Chef Chen had even mentioned a slave seal after. Even though she hadn't heard of something like this before, she knew that it wasn't anything simple.
Even though the current young Chef Chen was much weaker than herself at the moment, for some reason she felt that once she agreed to that, then she would lose everything.
Once she accepted that deal it was no different from giving everything she had to this young man that seemed like her last hope of saving her son.
At the same time, she was reminded of something weird, an expert was able to use mental communication only after they had gone through their 3rd evolution.