I’m not keen on the Tink is Belle’s mother theory. IMO it kind of takes away from Belle’s character. Instead of everything that happened to Belle being because of her choices, to help people, to see the good in others even if they don’t believe there’s good in them, etc, it would all boil down to Belle has secretly had magic all along and didn’t know it because she’s half-fairy.
I like the fact that Belle is just a normal non-magic girl who just so happens to have true love with the current dark one because she chose to see the good in him and not to give up on him. He fell in love with her because she didn’t see him as a monster, not because he could sense magic in her.
As for why Rumple left Belle with the cloaking spell instead of giving it to a magic user, I have a theory. Rumple wanted Belle to stay behind because he didn’t want her to see him die, because he wanted to protect her and because he didn’t want her to see him as “the dark one”. Rumple knew Belle wouldn’t just stay behind because he asked her to, she needed a reason to stay so he gave her one. He played on her good nature of wanting to help people and protect those in need, it was how they met- Belle sacrificed herself to save her people from the ogres, Rumple told her that in his deathbed phone conversation “You are a hero who helped your people”, Rumple knew Belle would stay behind to protect the rest of the town because that’s her nature.
All magic comes with a price!
Keeper of Felix