They're writing Belle kinda stupidly, imo. Here she is with amnesia, and she's asking Ruby--and everyone else who calls her Belle--"Why are you calling me that?" Well, Gold freaking her out aside, if you don't know your own name people who aren't acting creepy are calling you Belle and telling you that it's your name, it's highly likely they're calling you Belle because it IS your name. I don't mind the plot, I just wish she was written a bit better.
You'd think that when Ruby comes around, acting nice and seemingly familiar, that she might just ask, "Is Belle really my name? What else can you tell me? Why can't I remember?" I know, plot device. But silly. Belle can have amnesia, be calm, notice there's weird stuff going on around her, and still
be able to resonate with the stranger/texter.