Invite By Email -- Status of Email Addresses Submitted

I recently used Twitter's "Invite by Email" function to invite several customers to connect with us on Twitter. One of the customers who received an invitation contacted me and was extremely angry and distressed about receiving this invitation. She wants nothing to do with Twitter or any social networking site. She attempted ONCE to select the opt-out option in the email message, but got an "OOPS "message (she refuses to try opting out again). She is now under the belief that Twitter will bombard her with further invitations to join Twitter -or- send her email messages on behalf of advertisers -or- sell her email address to some spamming company. I tried to assure her that Twitter was merely acting on our behalf to invite her to join and connect with us, nothing more; she does not have to participate in Twitter in any manner nor is she now a member of the Twitter community, but the customer isn't satisfied with that answer. She wants assurances from Twitter that they will not keep her email address on file, will not try to contact her and will not provide her email address to anyone. I can find no statement to this effect on the Twitter website, nor can I find any contact number to speak to anyone at Twitter. Can someone advise how to contact Twitter and get some resolution? Or does anyone have any policy or information I can share with this customer to assure her that her privacy is not in jeopardy? Thank you.