That's the thing, the dev already confirmed she's going to be romantic with the Hero Version and not with the Normal Version, but will at some point discover that they are the same person. No need to wait and see, the dev already confirmed - she will not pursue romance with the MC because they are siblings, so she will pursue romance with Xeneg (which is a completely different persona, it doesnt matter if it's the MC).
If we follow the devs logic, that she feels weird about beign with her brother, when Xeneg reveals to be the MC, what should happen is Kate being angry the MC and then refuse to be with either of them.
This entire plot makes no sense at it's just jealousy baiting.