With all the flashbacks, Thana knew she could never talk about it to anyone. She instantly regretted sharing pieces about her memory and igniting the princess' curiosity al about it. Instantly she covered it up with a made-up story regarding her and a particular man. She took some details of past relationships she had encountered.
Again, she knew that she was becoming more and more dishonest about her life. It's making her feel terrible the more she went on about it.
However, that memory was supposed to be buried especially now that she was no longer in the same world as her mother. She would already cease to exist just as Thana had randomly disappeared from the world which she once knew. Things had changed ever since she had opened her eyes and accepted where she had gone.
It would have been easier if only her memories had disappeared as well. It was quite unfair that she had to keep every bit of memory about her past. But maybe there's a reason for it.