Hi Jennifer Heneghan,
Based on your description "all policys & procedures have been set up to allow for this", if you have the delegate permission for her mailbox, you can refer to below article to add her mailbox to your Outlook profile and then check her emails:
Manage another person's mail and calendar items
However, if you cannot access her mailbox after trying the steps in above document, then a possible reason is that your account doesn't have the correct permission to her mailbox. In this situation, if your account has the correct administrator permission, you can refer to below article to assign permission and try again to check the result:
Accessing other people’s mailboxes in Office 365
Please feel free to let me know if you have any problems when doing so and need further suggestions, I'll be glad to continue to help you.
Best regards,
Jennifer