If you're trying to get it resolved quickly, your easiest route is probably to call the Help Desk and get the two versions of the person merged under one profile on one person's account.
However, if you've got a few minutes and a computer, you might be able to resolve it... (If you have multiple computers it'll go faster, but if you're only working with one you can do it, it'll just require a lot of logging in and logging out of accounts)
First, all of this assumes that Mom is a "managed by" sub-profile under two people's accounts (we'll call them Person A and Person B) and both A and B have access to their own MDE accounts. If one version truly is Mom's own account but she doesn't remember how to get in, it'll be Help Desk required. I don't think it'll matter, but if Person A can see both versions of Mom, they should probably un-friend the version that Person B controls so that they only see one version (and vice versa). (Though if there's an active hotel reservation and/or tickets, it may not allow you to do this)
The next step is to have Mom (or someone acting on behalf of Mom) to go onto the MDE website to create a brand new account for herself using her own email address.
Then, Person A goes into their account and under their managed-by-them version of Mom, they invite her to be friends by using the email address Mom use for her account. Mom then logs in and accepts their friend request.
Then Person B repeats the process, going into their own account and filling in Mom's email address and having her accept the friend request.
When Mom accepts the requests, any reservations, Bands, tickets, etc that are connected to the managed-by profile should move over to her new account, and hen Person A and Person B look at their accounts, they should *hopefully* only see one version of Mom and it's the same one. Other adults with their own accounts should probably take a moment to friend-request Mom for future flexibility.
At that point Mom will never have to log into her MDE account again if she doesn't want to, since other people who are her friends can make reservations and link them to her.
Also note: This will only work for people who are old enough to have their own MDE accounts (age 13 or older). The Help Desk will be required for duplicate young children...
-Rob