See above. A mistaken age is a defense, not an exception for consent. As a 17 year old, the law says she cannot consent. If he says "she said she was 18", that does not make her 18 and able to consent. But he can try to use it as a defense. Given the alleged violence of what happened that night (perhaps after her sexual encounter with Araiza first), it might be a heavy lift for a jury to consider she lied to him and then was unfortunate too be raped by his friends.