She was lived in an orphanage before taken by Julian's family (guessing from the side story about orange soda), and yeah.. maybe that family got rid of her previous records. There are more than one child beside Angla, and we are not sure what are their purpose there.. they received education and the other children are dressed like Angla. Maybe something like a private owned orphanage?
The mansion is separated from Ouxili, so it's not Ming Lan's fault that she couldn't answer Ming Qing's question about that school.
I'm hoping that the damned old man fixed her family registry as "Shang Ming Lan", because it's pretty dangerous to her if she enter Ouxili as "Angla" (remember that Julian expelled students as he pleased and turned the school into a hell when looking for Ming Lan. Although it seems that my prayer is denied in the recent chapter T_T
Not just any spelling error either... Ming Lan aka "Angela" mistook Julian for an "angel" and tried to ask him if that's what he was, but due to a language and spelling barrier... Julian thought that was her name. (Julian also said she looked like an angel.) To her that name was apart of her trauma of being kept as Julian's pet or toy. The tattoo bound them as part of Julian's family's strange marking. Its like a brand(?).
btw pretty sure she was never in the orphanage system in the first place and that's why they cant link or trace her. unless she WAS in the system until she went into Julian's care and either Julian or Julian's father got rid of her "existence" or "evidence" pertaining to her.
(She's like a ghost child but Julian is her curse since Julian is the one who traumatized her)
╥﹏╥ Its all really dark honestly and heartbreaking. hopefully this helps a bit.