About the drama "Love at Seventeen" and Ai Li Si's amnesia?

I watched 3 eps of it and looked some videos on yout ube of other eps but I couldn't understand about this amnesia tag. Can someone spoil me about what she forgot from amnesia? Or is she even has amnesia? What happened in these 13 years? Please spoil me about this amnesia thing and her brain injury.

 Echo:

It's been a couple of years since I last watched it but I'll try and tell you what I remember. 

Something among the main characters in High School wrecks their friendship. They go their separate ways and then reunite as adults when the He Hao Yi  starts to work at the same company as the Ai Li Si.

At some time after High School, Ai Li Si undergoes surgery for something serious and a side effect/complication is that she (temporarily) looses some of her memories. I can't remember if it was an illness or an accident that caused her to have surgery. As the show goes on, He Hao Yi tries to get Ai Li Si to "unlock" those memories and the 2nd ML tries to stop him. 

I understand now. So she loses her memories after the surgery. I thought she had an car accident or something like that. Thanks for explaining!