Her portal fantasy was of Adora never leaving the Horde, not being brainwashed. The whole reason Adora’s departure broke her was because Adora made the decision to leave, and in her Catra’s view, didn’t consider Catra more important than a bunch of sparkly hippies she just met. Forcing her to forget all that wouldn’t make Catra forget the fact that if given the same choices and experiences, Adora would still choose the rebellion over her. Shadow Weaver wanted to brainwash Adora because her goals concerning her were objective, external. She didn’t care about how Adora felt outside of how she could use those feelings. But Catra’s issue was with Adora’s feelings, and artificially erasing them wouldn’t bring her satisfaction.
Catra didn’t consciously create her portal fantasy any more than anyone else did. It was something that sprang into existence based on her inner desire for an Adora that didn’t change her mind about her goals or her life, and stayed with her. And it was a shared fantasy with Adora, who on some level missed the simplicity and familiar comfort of the life she grew up with, and missed the Catra who wasn’t evil or her enemy.
But yeah, a huge aspect of Catra is her desire for recognition, which along with being tied to her insecurity regarding Adora‘s abandonment, is why a part of the fantasy was SW approving of her.
Which raises an interesting question - was that also, to some level, a desire of SW’s? An Adora that is living up to her designs for her, yes, but also the ability to show affection/pride for Catra? Not all aspects of the portal fantasy were wish fulfillment - Bow being a historian for example - but this was at the end of S3, when SW had already been broken down quite a bit, and she and Catra had gone through some twisted bonding.
It’s worth noting that people retained their memories from the portal, anyway.