She owns the copyright of "Wheel of Time" as a published and copywritten entity as the owner of RJ's estate, but I don't believe this extends to the idea of writing further stories in WoT. Other writers might seek her approval, but you can't copyright facts, ideas or theories.

In fact, depending upon whether Tor owns the book license, they could authorize any writer to write in the WoT universe. "Star Trek", for example, has many novels, games and material that were licensed without buy-in from the Roddenberry Estate.

We simply don't know if her ownership of the estate extends to the right to approve or deny future licensing requests, or if part of the negotiations stated some other arrangement. It is possible that the estate could have the authority to approve or deny requests without getting any portion of the sales, for example. Without knowing the extent of paperwork and rights in the series, I think we don't have enough information to ascertain legal clearances required to create further stories in the WoT universe.