I actually argued myself into a different pov on this one, so bear with me :).
I think we need to change the terminology from simple "consent" to "informed consent"
The medical profession, for example, consent is not enough, it must be informed consent.
So, you go to A+E with a sore wrist. A consultant appears and says he must cut your leg off. You say go ahead, you know best. Consent? Yes.
It is the Dr's responsibility to make sure you know why he is cutting your leg off, and the consequences of that action, or not, so you can choose whether to have your leg cut off, knowing the predicted outcome if you don't. The dr also has a responsibility you are capable of informed consent, not drunk, unconscious, mentally impaired.
Therefore in this situation I think it is both parties responsibility to have informed consent. He should make sure that she knows she is having sex with a man she hasn't met, and the risks she is taking. She equally, has the responsibility to make sure she is having sex with who she thinks she is, and if it turns out to be some 13 year old boy, that's on her.
So I think they were both wrong not to gain informed consent from the other party. But in this case it is him that does not have consent as he has not informed her that he is not the man in the photo- if he had told her that and she had still wanted to go ahead, then informed consent.