Parallel Susie looks very similar to her counterpart, with a few key differences. Her helmet, hair, and mech have a black and red color scheme. During battle, she fights without her blue visor for the first phase. The Haltmann Works Company logos on her mech are replaced with a logo resembling an eye; this logo is also present on King D-Mind's hammer, suggesting that she may be affiliated with him.
Spoiler alert: The following section contains plot-specific details.(Skip Section)
After many battles, Team Kirby defeats Taranza, the mage who has been invigorating bosses to attack Dream Kingdom. Peace is briefly restored to the land. This is cut short when a dimensional rift opens, releasing Parallel Susie. Narration later reveals that Taranza, who only feigned defeat, was responsible for summoning the rift and opponent.
End of spoilers
Parallel Susie is fought at the Decisive Battlefield after being unlocked for 120 Gem Apples. She is an Ordeal boss in the Tougher category and must be defeated before the player can access Parallel Landia. She attacks using some of Susie's techniques from Kirby: Planet Robobot. These primarily include jumping around, spinning her mech's arms, striking the ground from the background to produce shock waves, and firing missiles into the air.
This, partnered with the fact that Parallel Susie's fight uses the Greater Doomer music, may be a reference to how, according to Kirby: Planet Robobot, Susie was transported to Another Dimension and studied the Sphere Doomers while she was there.