Hi doctorjessie,
I would generally advise against using the same Auctiva account with two different eBay accounts because it can create complications with respect to the scrolling gallery, however, if your mom's account does not currently have any active listings that contain the scrolling gallery, you should be able to do this without creating any problems.
To associate your Auctiva account with a new eBay account, you just need to generate a new token by clicking the "eBay Settings" link under the "My Account" tab within your account, and then clicking the "Get New Token" link on the ensuing page.
Any additional questions or concerns? Please feel free to contact our customer support team using the appropriate link on out help page:
http://www.auctiva.com/free-auction-software-help/help.aspx-Mike