The reason only Barry could communicate with Gideon was because the prototype for this AI had been developed by the Flash from Sara's home universe.
Electronic lifeforms often had very peculiar operating logic when it came to their creators. Though this Barry was not that Flash, Otherworld Variants could still be considered relatives, right?
"Oh, I'll go take a look."
After hearing Deathstroke's words, Barry nodded eagerly and struck a running pose.
"You're not allowed to go!"
Sara hurried over, wearing nothing but a bath towel, her hair still covered in foam.
She stood in the doorway to the corridor with her arms spread wide, like a mother hen protecting her chicks, refusing to let The Flash near the ship's core.
"You didn't tell her we were coming?"
Barry looked toward Bliss. Batwoman had already retreated into a dark corner of the bridge, pulling her cape over her face and revealing only a pair of eyes beneath her mask.
"Maybe I forgot."
Bliss answered without the slightest sincerity. She did not know what Deathstroke intended to do either, and she wanted to gather more information while he explained things to Sara.
Barry gave an awkward smile and wiped his hands against the stomach of his bodysuit.
Just then, Deathstroke strolled out of the captain's quarters. He did not waste words, simply taking a seat in the captain's chair before saying in a low voice, "Sara Lance, I want to make a deal with you. I need you to use the Waverider to take Barry and me to a few places, pick up some people, and bring them to Earth-0."
"Slade, I thought Cindy was coming." Sara swaggered over. Despite wearing only a bath towel, she carried herself with the confidence of someone in imperial robes. "What can you offer me?"