There's a bit of difference between their lineage. While they are both fox, Su comes from a much stronger family. This is why she didn't reveal herself immediately with Tang Ran and why she keeps it a secret from others as well.
No no I dont think you understood what I said
Im talking about tang rans friend. Tang ran told her friend that su is a fox in previous chapters but then in the latest chapters the friend telling su that tang ran isnt human>su reveals her fox form> erase memory etc doesnt make sense with the fact the friend already knew su isnt human but talking to her as if shes is
In chapter 55 tang ran tells her friend I forgot her name that su is a fox so I dont get the part were the friend tells su that tang ran isnt human and then su reveals her identity and erases her memory.