I totally get this response, but I feel like nobody puts themselves in the position of OP here. Of course it is clear as day, but she's in fucking love with this guy. She's invested her time, effort and love into him and thought after a year it was all great. Now this drops in her lap and shits on everything, of course it's easy to tell her to run - we aren't the ones in deep here, she is.

In this situation, people are in denial and want to find every possible way to believe it isn't true while their heart is trying to catch up and get to grips with it. It won't last now, but you can't expect her to walk away at the click of her fingers until she has understood the whole situation and processed it.