Is this a Gmail account? If so, Gmail works a little differently than the email accounts that I am familiar with. Here are a couple of support articles for Gmail.... From Google and Apple.
And the Google search results that I found.
I assume that this email account is an IMAP account. She should be able to delete the folders on the server - on the web using a browser. There should be settings to add and remove mailboxes and folders in there. Any changes that you make to an IMAP account will be reflected across all devices. If the folders are removed in there, they will disappear from the iPad as well.
But ... Where did these folders come from in the first place?