Hello Kathleen,
Unfortunately, we do not have control over ClickDimensions Emails when they are forwarded, so the behavior you are seeing is normal. When the recipient forwards the email, their specific tracking code is still tied to it, which results in the Unsubscribe Link still being connected to the original recipient. There is not a workaround to ceasing this behavior when an email is forwarded.
You can submit a Feature Request here for forwarded emails to have deactivated Unsubscribe Links.