"DID" (Dissociative identity disorder), which used to be called Multiple Personality Disorder is the only "illness" which would allow this to happen.
However, what you are describing seems to be DDLG which is a subcategory within BDSM If you google/yahoo DD/lg you will find everything. There are videos on youtube, lots of stuff on Snap/Insta and many other places. Whild DD/lg is not common most women (and men?) are simply not comfortable enough to admit their interests.
I work with women who have BPD, C-PTSD;PTSD, BP and sever co-occurring mental illnesses (psychosis, dissociation and social phobia). I have also been involved in BDSM locally for a long time. I am no one special but you hit 2 interests for me. If you have any specific questions and I catch them later, I will try to reply.
For what it is worth within the DD/LG community many refer to it as "age regression". That is a clinical Freudian term. But as you probably know Freud was a bit of a nut. It is more a part of your/someone's personality and their are no negative connotations as there are with the term "regression"