Without seeing the physical stuff of what you are doing, you can "export as catalog" from your computer with all the changes you want to merge into your wife's computer.
Then copy that small catalog to your wife's computer and from her LR catalog, "import catalog" to merge your data changes with her catalog.
Since you both have the files on each of your computers, there is no need to include those in the "export as catalog". After the import of your changes, she might need to "relocate" the files by pointing to them on her hard drive.
If you are both working on the same files as the same time, the "import from catalog" can get tricky about what to do with mismatched data.
Hi ManiacJoe! Thanks for responding!
Well, I tried that and it didn't work for some reason so I thought I had just done something wrong.
I uploaded them to my LR. Culled the photos. Selected "Export this folder as a catalog". Reattached the mobile drive to my wife's computer. Selected "Import from another catalog". The images merely loaded under the hierarchy of the mobile drive rather than transferring them to the internal Macintosh drive. I tried making sure that the necessary wedding was actually highlighted, then tried "Import from another catalog" again. Nada.
Your exported catalog has the paths for the files either pointed at the external drive or at your hard drive. But they are just paths.
After you import your catalog into your wife's catalog, use the "update folder location" command in the Folders panel in the Library to point the folder to your wife's hard drive where her copy of the files already exist.