Hello.  There was this kdrama that my mom was talking about. She want to watch it again but she forgot the title. All she can remember is that the Kdrama is about a single mother (?) who was engaged or had a CEO boyfriend, but her boyfriend's mother was against about their relationship. The boyfriend's mother needed a kidney transplant and the girlfriend donated her one kidney. The boyfriend got amnesia. My mom think they got separated because of that, she's not sure.

After that, the girl became successful and owns a construction firm.

My mom only remembers 2 names from that kdrama, the mother and daughter's name; Eunsol and Summer

She watched it on Arirang TV Channel in Hong Kong, maybe around 2012 - 2013 

Maybe I'm sorry, I love you 

It is a very old drama but it has some themes that you mentioned.