I like the idea that Regina has her heart locked up in a box, (well, not like it, coz it’d be super sad, but I like it as a plot point). There wouldn’t be any brainwashing needed because Belle would be numb and wouldn’t remember anything of their love.
That may very well be the case. We’ve been speculating for months about who’s hearts are in Regina’s volt. We’ve gone from David, to Kathyrn, to Mary Margaret and even Mr. Gold. But the most plausible and sensible choice would actually be Belle. We know for a fact that Regina has her locked up. We’re not exactly sure why, but we do know it’s for a very specific reason that has yet to be revealed to us. So, Regina taking Belle’s heart actually makes more sense. Regina probably has the hearts of all her slaves and victims, so there’s no doubt in my mind that she has Belle’s. And on top of that, taking Belle’s heart and controlling her would effect Mr. Gold. When Mr. Gold finally finds Belle, he’ll probably expect her hug and kiss him, but sense Regina has control of her heart, she’ll probably pull away and declare her hatred of him. That would unhinge him. But that’s exactly what Regina wants. An emotionlly vulnerable Mr. Gold equals an easy win for Regina.