First, have your mother create a WikiTree account membership and then have her connected to her specific profile (or you can assist her if she's not very technically inclined).
Once she has a that done, don't forget to go through the process of going from a Guest Membership to a full membership.
Then the following process can be accomplished...
Take a look at the following WikiTree Help Page links that are specific to your question....
... But in short, you don't just simply upload it to WikiTree itself as WikiTree utilizes a (trusted) 3rd party that links the applicable DNA information via the following GEDmatch link (registration there is required and its Free).
You then just follow their instructions to upload your DNA file and then you just have to add your GEDmatch ID info within the WikiTree DNA Tests page to link them.
Issues regarding GedMatch is not managed by WikiTree, but GedMatch themselves.
If the above links nor GedMatch is helpful at all, the following answer provided within a similar/same question (asked within the WikiTree G2G forum) is probably your best bet to figure out what's going on.
I do wish you the best of luck! :-)