I can imagine how finding this out has really pulled the rug out from under you, but try not to assume the absolute worst. She's not lied about every aspect of her life I imagine, but some major things. It sounds as if she did this in order to cover up feelings of shame and /or guilt, because she failed at uni.
These feelings are probably stronger than ever now, and combined with the shame she'll soon be feeling when she finds out you know she's been lying, that may well be very, very hard for her. It's hard for you too, but her lies came from a place of (I imagine), weakness, fear, shame and wanting to please people.
Be kind to yourself and also her. Be gentle. Listen. Try not to accuse her of everything without acknowledging that she's probably feeling terrible about lying. Love is the most important thing in the world, and her lies are weaker than that. Try to be strong and support her. I know you feel confused and hurt, but you can get through this. Maybe tell her that you know that things are not as she's represented them, and say that you'd like to declare a sort of 'amnesty' on lies, encourage her to come clean and feel massive relief. Encourage her to trust that you will love her and accept her, no matter what. You could do this with a letter, that might be easier for her and you. Sincere good luck to you.