Faking the email address an email appears to originate from is actually incredibly easy, spammers do it all the time. There honestly isn't a whole lot you can do about it, it is just as easy as writing a fake return address on a letter.
The only way you can effectively prevent someone from sending emails in your name, is to sign your emails with a digital signature. Such a signature cannot easily be faked. This method however, requires the recipients of emails have software installed that can verify the signature, so it is more bothersome.
Being able to send emails that appears to be from your friend and having access to her email account is not the same thing. You can fake the address without account access.
If she believes someone has access to her account she should change her password (and any password recovery questions) ASAP!
P.S. For future reference please don't post in the FAQ section of the forum. This section is only for guides, not questions.
I'll ask a moderator to move it so you don't need to create a new thread.
