Multiplicity

I think you're right on target about how this "happiness" isn't really happiness, but something else entirely. If I were you, though, I'd try to explain things to the person whose memories were erased, so that she knows what's going on. If she agrees with you, you may even have a better chance arguing with the one who did the erasing, since then you'd be able to argue, without contradiction, that it wasn't what SHE wanted at all.