which one? Do you mean the “horse” memory?
Yep. Did she put it at random into several people to gather “followers”? If so, she knew who she was alll the time…
I always had the idea that it was just her way to create those memories: she would make up a fantasy that let her feel as if she was not locked in that room, trying to make it as real as possible while using elements from her own memories which is the reason why her “made up” memories look so real.
The memory he had implanted in his brain was a variation of Stelline’s childhood memory, and when he shows up at her place she tells him:"This is not a fantasy"or something like that because she knows it’s not.
I think she didn;t spend her whole life there; she had some childhood, then while she was still a kid her parents locked her up in order to protect her.