I urge everyone that finished the show to listen to the only audio drama translated in English, you can find the rest of untranslated ones on nico by namesearching in japanese.
https://youtu.be/KTjHDblZsAAI liked the ambiguity of the show not giving us a concrete answer on
Key and Sakura being half-sisters or not, because the show had already showed us how much she cared about Key. I know most read it as as romantic because of the Lain-Arisu parallels, but the frustration of not understanding and the disconnect she felt and YET going out of her way to help Key achieve her dream felt like a tired big sister trying to make her fucked up little sister be happy, even when she was struggling with her own shit. I may be projecting though.