The username in the order form? You can add/remove users with "operator" permissions. The username that you inputted when ordering shouldn't affect much. https://www.hosthorde.com/forums/resources/operators.47/
She said that owner permissions are different then admin. I have no clue how that works. If there is no difference with permissions. Then its not a problem.
Is this a CraftBukkit/Spigot or Vanilla server? If it is CraftBukkit/Spigot and using permissions plugins, it depends on your configuration. If Vanilla, there is only Operator and non-Operators.
OK I think its vanilla and thats what I just did for her was made her a op. I think that gave her most of the permissions.