Why is the invitation asking the client to close the the CRM account?

Why is the invitation asking the client to close the the CRM account?

I have opened up an account for my client, and I tried to invite her into the Zoho CRM to use her own logins, and as the company, we would have the main logins so that we can make sure leads are going in, etc. It seems though, that when I send her the Zoho CRM invitation, it asks her to delete her CRM account, and then click on join the account. Why would it ask her to first delete it and then join? It doesn't make sense. Please help me