All I wanted to do was share a calendar with my wife.

All I wanted to do was share a calendar with my wife.

I currently have a gmail calendar that my wife and I access, we have it on our android and iphone and use thunderbird as a client. I decided to use zoho calendar to replace this as we have mail here.
We have a domain with imap with individual accounts. I cannot find a way that we both can access the same calendar using thunderbird.
I created and shared a calendar exclusively with her account with all rights, but I cannot get it to connect. Her rights will not connect to the shared calendar and you cannot use alternate credentials. How do you do it?  A group calendar will not allow user delegation.
I don't think it can be done.