I said this elsewhere, but I'll say it here too. Your girlfriend should not have to adapt to society to feel less socially awkward. The world needs to be more accepting of people with issues like that. It shouldn't be socially awkward. It should be okay for her to just say "Hey, sorry, I don't recognize faces without context. Where do I know you from?"

I had a friend years ago with aphasia and I would help them out when we'd meet by telling them what I'd be wearing and be on the look-out for them so I could walk up to them and they wouldn't have to pick me out of a crowd. I'd also usually greet them with my name. They were really good at identifying voices usually, but the small effort was always appreciated, and it's not that hard.

Their aphasia also extended beyond faces, so they would often have problems finding their car if they didn't park in the same place, so they would take a picture of the car and some landmark near by. They would show me the pictures so I could help them find it.

What I'm saying is, is we as a society are going to be social to this great of a degree, where we interact with dozens of people, we need to learn to make it a place where everyone can also be involved as they are, not force them to conform to impossible standards for them.