I finished watching Steins;Gate and Steins;Gate 0 anime. Suzuha first appears in Steins;Gate alpha world line, where Daru dies in the future(I forgot what time but probably 2025), so Suzuha follows her mom Yuki’s last name Amane somehow. But Daru lives in the beta world line until 2036, so shouldn’t Suzuha uses Hashida as her last name in SG0? I don’t recall Suzuha ever introduce herself as Suzuha Hashida, even though she’s Daru’s “sister”, but the cast list in the ending shows Suzuha Amane.
Well I don't remember that they call Suzuha: Suzuha Amane even once in SG 0. I think in the beta worldline they always call her Suzuha (without a surname). Maybe the cast list is just wrong. Still, there is a possible explaination, maybe Suzuha just use her mother surname. It's not a rare thing.
Those are just speculation since I'm not sure they even address it in the VN (at least I don't remember them addressing this fact).