Cannot properly add new team member to private S3 bucket

A new team member has joined my company and I'm trying to add her to the private S3 buckets I've created to store company data. I've tried several methods including adding her to my organization (successful) and giving her full perms on the ACL of the bucket itself (also successful). However, she is still unable to access the data in the bucket nor see the bucket on her "Buckets" page in S3 nor change any permissions within the bucket. Is there a proper way to add a team member such that they gain full access to it like the admin? Thanks!