Because she really did have her memories wiped and Tav would be taking advantage.
Eh, I see her more emotionally closed off/cautious than Tav being considerate; Tav can ask questions with very clear innuendo, and she very clearly shuts those innuendos down. Shadowheart isn't a fair maiden that needs protecting, she's an emotionally strong character that knows what she wants, even if her memories are patchy at best.
You can disagree if you want, of course. It's not like disagreeing will break anything.