Who should walk me down the aisle?

It's usually just the father of the bride that walks his daughter down the aisle. Your mother said she would feel uncomfortable, so please, don't do it. She will be the first to be escorted to her seat when the ceremony starts, with her husband walking behind her. Then your father's wife. Then your bridesmaids, your maid of honor and your flower girl then you and your dad. Your mother's probably gave this a lot of thought since it is your wedding, and she's probably doing a lot already just being cordial to your father and his wife during the rehearsal dinner and at the reception as it is. It would look really awkward to have both walking you down the aisle, as the focus of attention will then not be on you, everyone will be looking at them. Plus, it's just the father of the bride. (Or an uncle, a brother.)