Ok, I need some more info. So there was a person who hacked into your friend's FB account, and you need to hack into it to get it back, correct? Or you just wanna hack into your friend's FB account for fun (also a valid motive.) Well did the hacker change the email for you to change the FB account password or did your friend forget his email password. If the hacker changed the email to his email, what you can do is try to setup a phishing page.
Trying to get her page back. Not to hack her account for fun. I think the hacker changed address, or just password. Because nonE of her emails work. - including 2nd primary email. What I like to do, is to hack into her account, have it under my emails and give her the details so she can log in.
Also before you go doing "illegal stuff i guess," try this: digiwonk.gadgethacks.com/how-to/get-your-hacked-facebook-account-back-0147366/
I have came across to the link before, but the tricky part is the security questions and choosing 3 friends. I like to by pass that if I could.