Idk if it has a name or why it occurs but I’ve seen it in a few autistic people. I did it as a child but stopped. There was a girl at an autism summer camp I went to who still did it as an older teenager. For both of us the “solution” was just to call us by what we were calling ourselves. This is much less likely, but is it possible the other names are actually alters and she has a dissociative disorder?
Are they obsessed with any media w main character named Grace? If there’s nothing else going on then I would just call this Certified Silly Goose behavior, AKA nothing to be concerned about. Sometimes I get stuck in third person w my chosen name, sometimes I get stuck in 3rd person w “ya bitch”, sometimes I get stuck w a clone high JFK accent 🤷 Coulddd it be gender exploration? I asked loved ones to call me by my chosen name before I officially decided to choose it bcos I wanted to try it out
From the quote you gave it sounds like they’re either at work or doing chores, so it could be an intentional dissociation to make work/chores easier. I have a cleaner named Vanessa that’s just me with a European accent and she LOVES cleaning and I pay her well and really appreciate her, and she’s nothing like Alex (who is actually me) who just wants to lay on the floor and cry
she has multiple OCs which she will become obsessed with each at different times and roleplay as (like in a roleplaying setting online) and then it kind of carries over to real life if that makes sense. we’re both trans haha so i asked her directly if it’s gender exploration, she said no. i do wonder if it’s dissociation like you said though.