I don't think Mabie would be a very nice nickname because it'd sound just like maybe.
To my ears and eyes,
Mabel clunks. Rhyme label, table, able, cable, stable, gable... clunk. It clunks so hard because all the -able words are so homely and sturdy and workaday. Makes me think of a homely and sturdy and workaday person.
Maybelle (stress on the
May part) seems nicer to me, although it looks silly.