My photographer friend is trying to send me a catalog from her lightroom 5 so that I can edit for her. The issue is that I have lightroom 6 and it is not allowing me to open it because hers needs to be upgraded. Is there a way of going around this, so that she does not have to update to lightroom 6?
It's possible to update a catalog to a newer version, but there is no provision for going back to a previous version. You could save changes to XMP, and send the images and the XMP files back to the other person. But there's no way you can work on the catalog and then send the results back to the other person.
The issue is that I have lightroom 6 and it is not allowing me to open it because hers needs to be upgraded.
This isn't the issue. Lightroom 6 can indeed open Lightroom 5 catalogs. If you are having a problem opening this Lightroom 5 catalog, please state in great detail what you are doing and what happens. Please quote any error message exactly as it appears, unedited, complete, word-for-word.
Also, if you owned Lightroom 5, you could simply use that for all the work with this client, and all of these problems are gone.