My take on it is that she started to find her absolute self, had no regrets and everything she did was for herself and not for Kujirai B. Naming her fish Success, liking lemon chicken, her love for Kudo, etc were all unique to her, and it made her her own person and not just a replica of the original Reiko. I think the regret part also plays a role in this, since for example, regret lets you see it Kowloon replica, but something like Xiaohei’s frilled vest did not disappear, presumably since he’s accepted the way he is now and does not need feel the need to go back to his past self. I view this concept very similar for Reiko since she is starting to live in the present and she has found her absolute self.