Tasman is a bespoke clone that Ultana bought secondhand at the black market, when she was left for dead. Basically she acts as one of Ultana's companions for now, until she gets trained to do something else.
Here's the thing, those personas were basically wholly different people - it was difficult to see Eurus in the others even after we knew. Playing different characters is an actor's JOB, and I don't think she ingeniously linked them together or anything. I might be being unfair, though. She was a good actor, but it might've been spoiled a little by my utter hatred of the last episode.