Her sister gave me some info, check out her account YourLittleGlaceon.
MiaUsagi aka My Inner Anxiety is an abandoned account since Mia died in real life in 2017. MiaUsagi's account strangely got activated again. Mia's sister didn't know who was on Mia's account, the person on their account only goes by My Inner Anxiety. YourLittleGlaceon did try to get back in the account but the password was changed and the email was changed. So far, he can only be tracked by the decals he makes. Through one decal he appeared to be stalking someone.