Before opening the attachment, Natasha should not disable her computer's firewall, and she should not open the attachment without any hesitation. The safest course of action would be to scan the attachment with antivirus software or use an email service that automatically scans for malware.
Forwarding the email to colleagues for their opinion can be helpful, but ultimately, she should ensure the attachment is safe first. It's also advisable to verify the sender's email address and check for any signs of phishing.