Given that Elio made the comment, I tend to think the controversy relates to something within the fanbase. When I hear the phrase "controversy," I think more about something that would challenge or re-enforce people's perception of the character in a major way. That's why I think it could relate to her beginning to poison Robert, or outright killing him. That would completely challenge her character thus far and lead to some ugly debates/arguments. So far Sansa has been an innocent idiot, and her fans tend to think she's going to become some major player of the game. Having her poison (or smother) Robert would be a continuation of her being Littlefinger's puppet, but to the nth level.
I don't see Littlefinger abusing her, she is far too valuable; raping her would hurt his plans to marry her off. Personally I don't think the grand plan he told Sansa will happen, but I still think he'll be working towards it. Sansa has to be "pure" to marry Harry, and then at the wedding she can reveal her true identity. I tend to think that plan will fall by the wayside, either due to Harry dying or Littlefinger perhaps deciding to roll the dice on a marriage to Aegon.