Dear Picho,
you can delegate approvals to another user with "Manager Delegation". Beside that the alternate approver needs the proper authorization to approve (authorization must be given) an access request. Check in SLG1 the authorization which is missing for the secretary and what has to be authorized.
Authorization does only mean that the baseline is given to approve requests. Without a proper delegation no one can approve the request.
Let me know if you need more in detail.
Regards,
Alessandro