...how did she not recognise a whole ass dude she was in love with and had sex with?

Asking the obvious here... It was along time ago, all those years apart and you expect her to be hung up on the same guy?

Being hung up on a person and basic facial recognition are two different things.

Like I said it was along time ago, she just forgot. It's not exactly impossible or unheard of to forget someone you once knew...