When either my wife or I am logged in, we are kicked off if the other logs in.
Correct. If you both want access to the cameras, you need to create a "friend" account.
My wife has alreadybeen added with access and her email. Still no go.
If you are using different credentials, then you won't be logged out when she logs in.
There is some friction in getting the friend access to work.
The first barrier is to make sure the invite was accepted from your account. If it shows up as pending, then have her open the invitation email on a PC (not a mobile device) and click on "create account" again. That will open the browser to my.arlo.com. Since she already has an account, she just logs into her existing account. That should result in the invite being accepted.
The second barrier is that Arlo is currently migrating to a new user interface. Honestly, that isn't going well, so the migration is mostly paused as they are dealing with bug fixes. But for friend access to work, both accounts need to be on the same user interface. (Note the current app supports both interfaces).
The old interface shows "Library" as an option on the main app screen. The new one shows "Dashboard" and "Feed". If the two accounts are mismatched, you need to migrate the one showing "Library" to "Feed". You do this by using "add device" to add either a Pro 5s camera or a Home Security System. That will fail if you don't have one. But the process will prompt you to migrate to "Feed", so you can just stop after that happens. Note there is no way to migrate back to Library.
If she is using "Feed", then at that point she will see two locations in her account - both labeled "home". One will have the shared cameras, the other will be empty. You can rename locations, which will reduce the confusion.