First, you need to ensure that your mother is listed in the reservation. You cannot use ME as a luggage service.
Second, if she is on it, what you can do is use one of your tags; cross out your name and put on her name. Do not go through the scan code, since it contains all of the info regarding your reservation and your resort.
We had to do that one year, when we added a fourth person to our reservation a few years ago.
Believe it or not, while we were checking in at the desk (back when everyone had to go to the desk and check in) and the CM asked how many bags we had - I told her four and she said, oh yes, the one with the name written in marker. They had already retrieved the bag and it was already in the system.