If a collaborator is trying to open a timeline via the invite link, but it is loading for more than 1-2 minutes, you can try revoking their access and then re-inviting them to the timeline. This usually helps refresh the access and resolves any loading issues.
To revoke her access:
Go to the "Collaborate" tab within the timeline and find their name in the list of collaborators
Click on the three dots next to their name
Click "Revoke Access" button next to her name
Re-invite them by clicking the "Send Invite" button
If the issue persists or if you need any further assistance, please let me know, and I'll be happy to help you troubleshoot and resolve the problem.