I don’t know if I think she has Belle’s heart. I’m inclined to think that Regina realizes that Belle is special to Gold and, as strange as this sounds, ripping people’s hearts out and keeping them in her vault seems like a very average every day thing for Regina to do. I would think that she would want to keep Belle “whole” if she wanted to be able to use her as a pawn to get Gold to do what she wants. I think that already taking her heart would be somewhat anti-climatic, I think that the implied threat of what Regina has the power to do to Belle since she has her locked up would be of more concern to Gold – especially since he already thinks she’s dead. I would think that “Surprise, here she is – just as perfect as the day YOU kicked her out of your castle so that I could capture her and keep her locked up all this time would be much more effective than, I have had her all this time and I ripped her heart out and now I control her just like everyone else in this town. I think that Gold would be more likely to cave to Regina’s requests knowing that Belle has the potential to be with him exactly the way she was before he kicked her out, rather than knowing that Regina has already had her heart ripped out – I think that would just make him beat Regina with his cane.