I must have had overstay at least 10 times in last 20 yrs, never more than 2 days and never ever been mentioned at immigration. Maybe you were just unlucky 🤷
to be honest I never asked much about the whole process. She just needed to have X amount in her account for a certain period not to long. She has 2 children and a job in a Korean restaurant to return to , it all seemed very straightforward no problems with anything at all. I hope u can get something sorted soon 👍