Why not wait until we see the conclusion of the matter before forming full-throated opinions?
No reason at present to assume it won't add to her character development. Every time you type or quote someone saying the word, "assume" you need to understand it just makes people more annoyed. Let it play out and offer your critique after the final stanza has played out. Otherwise, you just look like someone who has paused a movie a room full of people are watching in the middle to go on a long diatribe about something that may not even be an issue by the end.
Again -- I've stated why I have no faith in the showrunners to execute said plan, why I think the narrative structure of Game of Thrones makes such a thing unlikely, why I would be pleasantly surprised if such a thing did happen yet also my annoyance that "rape" would be the thing that turns Sansa into a STRONG character.
She willingly put herself into a situation where she would be raped by this awful human being. You can ask yourself what it says about her character that she would be willing to do that, knowingly having a choice to even go back to Winterfell. You could ask how these self-destructive acts could shape her character down the line, not too different to how Cersei may have been hardened by her years with Robert Baratheon. One of the show's major themes is the fluidity of power and subjugation. Her forcing herself into this game is going to have an affect on her as a character, we just need to see how it's going to play out.
What was her choice, though? What happens if Sansa says no? I can't imagine her living much longer. It's not like she's between "well, I can stay in the North and maybe get my kingdom back if I marry this man" or "I flee and be safe!" since, at this point, there's nowhere to go. She didn't really make a choice as much as confirm the only option that she had.
Which, again -- why put the wedding this early in the season? I'm dubious on whether this will actually be dealt with in the next few episodes, so it comes across, at least now, as an excuse to have something HORRIBLE happen to Sansa that I'm worried will never be dealt with.