@privatebanker : Why do you maintain that: “It’s a non issue in this case.” ?
(What are you referring to as the “non issue” ?)
OP: How much money is in the joint account owned by you & your mother ?
P.S. Any money held in a joint banking account is the property of each person listed on the joint account unless there is a clearly stated restriction–which does not seem to be present in OP’s case.