What I would do is add a "Remove from flow" flow step right before the "Send Email" step with the criteria needed to not send the email (ex. Lead Status is Nurture). Then leads with that lead status will be removed from the entire smart campaign flow.
Alternatively, if you do not want the lead to be removed from the entire flow and only skip that send email step, add a choice condition to the send email flow step (ex. If Lead Status is not Nuture: send email. Default: Do Nothing).