My iPhone is asking for a password for my CalDAV account when syncing my Google Calendar with my Apple Calendar; I don't think I have one and don't know what this is.

This question is actually for my boss who is having this issue. She logged into her Gmail account and is trying to move her Gmail calendar items into her Apple Calendar. She had her calendar set up like this on her old iPhone and is now trying to do the same on her new iPhone. Every time she tries to turn on the Calendar in her accounts it prompts her to enter her CalDAV account password. To the best of her knowledge she has never had a CalDAV account and has tried all of her most used passwords without success. What is this account? How can she figure out what the password is? And is there any way to avoid entering this?