If the home was jointly owned, the Estate of the deceased would be co owner with the spouse. If there was a will and the will passed the share of the deceased in the house to the spouse, the will would been to have been probated before the spouse became sole owner. The key answer would be whether title was transferred solely with the signature of the mother Otherwise, both the joint owners (your mother and the executor of the estate). would need to sign over title. If your mother was also the exectutor, a distribution deed would need to have been filed before she became sole owner.
