Kudos to OP, this is a far more interesting topic on Sylvanas than “Sylvanas did nuffin’ wrong” and its counterparts.
Sylvanas, as a character, has developed over time. She, through the circumstances she has faced, the nature of undeath, or a combination of both, has become increasingly harsh and pragmatic, though she naturally was so to begin with.
She generally rejects sentimentality, and encourages the Forsaken to abandon ties to their old lives, yet she herself has moments of both- her sisters, Nathanos, the locket- even her reaction at Teldrassil. This wars against her pragmatism and fear of oblivion, and makes her a hard read. Is her speech in Silverpine about the Forsaken genuine, or just mortar to the bulwark?
With Arthas’s death, her (justified) emotional hatred of him concluded after a fashion, and the events of edge of night, she tilted more towards her pragmatic side, and, by design or coincidence, seems to have marched ever more towards rejection of commonly held moralities.
I think it entirely possible that Sylvanas, as she is now, or at least if following the trajectories she is following, could attack Silvermoon. Even if subconsciously, it would be killing her own sentimentality/weakness, though that would never be her actual reason for doing so- it would require a pragmatic motive.
And that would be the Arthas parallel- not just physically attacking Silvermoon, no- but the equivalent of Arthas tearing out his own heart. That would be the act which showed her willfully abandoning what she once was in pursuit of something else, though, perhaps like Arthas, there might be some strange remnants left buried that determine or influence later action.
It would be an interesting path to take, though certainly a villainous one. While I don’t necessarily need to see her made into a villain, I’d prefer it to a “We are free, I was playing 4d chess, I’m really a goodie, never mind all the genocide” ending.