Like, this is what I get when I go to reply to an email, and hit the paper clip.
Wait, are you using your mail through the Gmail app? That might be the issue.
Can you not access that account through the native E-mail manager that came with the device, rather than the application? I know I have a Microsoft Exchange and a regular Hotmail account that I'm managing with said application, and it gives me the same file sharing options for both accounts.