The person who said it would be controversial later clarified that it would only be controversial to "certain quarters of the fanbase" or something like that, though.
I think LF raping her or Sansa killing LF/Robert would stir the entire fanbase. So I think it'll be something more subtle, like Sansa simply deciding to do something that may shock some people or ... something.
I've been reading more about theories about Sansa, too, particularly about her memory lapses/being an unreliable narrator (sorry if all this has been discussed .__.). Lots of people seem to theorize that Sansa is purposely repressing and leaving out events occurring to her in the Eeyrie (possibly hinting at more of a sexual relationship between her and LF? ... maybe the controversy?). Some people also think she was tortured more than we're led to believe in KL, too (and that she's repressing the memories of them), but in KL we also had POV chapters from Tyrion and Cersei (so I think it would be more obvious if Sansa was lying about stuff), whereas in the Eeyrie, the only person POV we have is from Sansa, so it's more difficult to discern whether she's lying or not. Pretty interesting imo. :O
I just want Sansa to finally do something. All the other original POV characters seems to be going somewhere with their storylines, but where hers is going is a lot less clear.