I know, it would be very wrong if he was to have a love intrest! And remember, DD said that Voldie pretty much isn't able to love, he hates the idea of it, and that is what Harry has that he hasn't... so he can't ahve a love intrest, right???
Maybe that's what everyone else called her, so he did to???
i know that voldie doesn't exactly have people he likes, just mayb those who he favours more than others. and most people call those they are closest to by a nickname, so it may be just that.
so he probably just is liking bellatrix more at the moment, and thus bella.
*Bella*, i did not noticed, that is cute ... Anyway, as long as Bella does not give her Dark Lord some *Voldie*, I guess their relationship is uneven, somehow