Hello,
I don’t see any posts and see that you have the redirect for that link. Unfortunately, as you can understand from this post https://support.google.com/webmasters/answer/47334?hl=en theme author can’t set what links to show there, sitelinks are automated.
I have removed the old admin from your site with the username that is almost the same as the site title and I suppose it could be the reason why google added it to your sitelinks. You can check the new username in private area above. And try to use the google removal tools again.
Regards