A crossover of my StS and *lizsama's Duality; this version of Sally comes from the latter.
I wanted to draw something fairly emotional from this concept, and Sonic Rose's interactions with Duality!Sally seemed like a good fit. Sonic Rose cares a great deal for his Big Sis, and seeing an alternate-universe counterpart of hers in the situation she's in, at "his" own hands no less, would utterly break him. So naturally he'd beg Sally to follow him back to his Mobius, at least until it's safe to return to hers...but it's not that simple (I'd imagine).
Would he be able to accept that? In time, maybe, but definitely not right away.
As for Duality!Sally--I'm not sure how she'd feel about a version of Sonic who didn't and will never become anything like the Dark One. Or having to explain to him why she can't go with him, for that matter.
Despite -everything- that Sonic's done to her, Sally still loves him, which becomes terrifyingly evident as the story progresses. I think the reasoning she'd put to not going with him is simply that her disappearance from this world would drive Sonic fairly mad. She'd be afraid for the people she loves and ultimately that would be her firmest standpoint. She'd kiss StS!Sonic there on the head and ask him to never forget how much they love each other. (Which, given the fact she's boning Sonic in her universe..might be awkward for StS!Sonic.)
Technically the concept of another Sonic wouldn't be new to her since she went back in time and met her and his younger self and watched them interact. The idea that they're just siblings and not something more would bother her in the sense that her love would be leaned towards that of a lover and not of a sister. It would also, I think, move towards confirming her fears that she's the reason Sonic became Darkie. Because as far as she's aware, Sonic grew up without her influence of love or relationship and he's doing just fine without it. Certainly not evil, at least.
It would probably he awkward for him, yes, though depending on what point in time this scene takes place at, he might understand that the differences between his world and hers aren't linear (Miles'd be a good indicator).
In regards to Sally being the reason her Sonic became the Dark One, Sonic Rose would definitely want to convince her otherwise, even if he didn't know much or anything of how that happened.
Which without that extra bit of knowledge would probably fall on deaf ears. :/ TECHNICALLY she was a serious driving point, but that's because she was indecisive in her stance with him and he got butthurt.
Technically the concept of another Sonic wouldn't be new to her since she went back in time and met her and his younger self and watched them interact. The idea that they're just siblings and not something more would bother her in the sense that her love would be leaned towards that of a lover and not of a sister. It would also, I think, move towards confirming her fears that she's the reason Sonic became Darkie. Because as far as she's aware, Sonic grew up without her influence of love or relationship and he's doing just fine without it. Certainly not evil, at least.
In regards to Sally being the reason her Sonic became the Dark One, Sonic Rose would definitely want to convince her otherwise, even if he didn't know much or anything of how that happened.
TECHNICALLY she was a serious driving point, but that's because she was indecisive in her stance with him and he got butthurt.