Because she’s the most powerful of the NPC teammates. Her overall stats are higher than everyone else, has flight that works in space and underwater, the immovable modification, and regeneration.
It’s hard for me to say what happened with your playthrough. I did two tests to recreate it, but I’m not sure what all powers you had.
In this test the MC has only stat boosting powers, nothing else. I didn’t optimize the stats like I should have, but still a 6 is rather good for just stats as the powers.
Then I turned on the max stats cheat and got a 20. Once more, the only superpowers this build has is super stats.
He’s slower than max speed.