Your friend should be able to interact with Withers and shelve your first character while you're offline.
Not sure if this will let you then make a new character with your second account, if that account has already been associated with that character.
But, if the only thing that you don't like about the character is their looks, then it would be easier to use the magic mirror in camp to change your appearance. You can't change your race, subrace, or body type, though.