It's up to your girlfriend now. She has to make the decision and as hard as it is for you, you can't impact her deicsion or get in her way at all. There a few positives - you told her, she didn't find out from another source and you're obviously devastated and she will be able to see that.
Answer any questions she has. Any amount of detail, don't hide ANYTHING if she asks you for it. if she decides to forgive and stay with you, then it will still take time. She will cry randomly, she will react badly to you saying you love her, and you'll never be able to say 'I'll never hurt you' ever again.Your relationship will never be the same. Let her have acess to your phone and emails if she needs or wants them. it will give her a little control back if she wants it.
Then you have to start forgiving yourself. Accept that people make mistakes. Never speak to the other girl again. Ever, for any reason. Know that you really love your girlfriend and that there were no positives from your actions and that your gf deserves to be upset and is allowed to be irrational. But also understand if she decides to forgive you that she has made her decision and you should respect that - don't constantly be in fear shes about to change her mind because that's questioning her strength of mind. Don't try and double guess her!
If she does split with you, well you made your bed and you have to lie in it. At the end of the day you should have thought about your devestation before you cheated. Think about how your gf feels, she never asked for the hurt, she just got lumped with it. You had a choice about ruining your life, she didn't. It's a terrible injustice. You will get on with it, you will get over it and find love again if you need to.
This is coming from someone who was cheated on by their partner who confessed and was devastated by it. He was physically ill for weeks before and after he told me. I chose to forgive him and were buying a house and going to get married.
Ultimately I feel sorry for your girlfriend, the dynamics of the relationship will completely change. She would feel more insecure with herself, there will be questions and possibly over thinking. Hey she probably feels her religious values are the faults and blames herself for you straying. The only thing i hope she has a strong will to overcome the negative feelings that will come, she has a good heart. don't break it again, the fact she can forgive shows a lot, forgiveness doesn't come easily when being betrayed.
Revenge, hate and anger is awful to go through. The amount of emotional torture can easily break down a persons will if they are not strong enough. Confidence is shattered, questioning your own core values and ultimately destroying yourself. I really Hope it doesn't go through this stage for her. I really do. It takes a lot to recover for most people but for some it will take years.
She never asked for this, when you and your gf started the relationship, you knew in the beginning about her religious values, you knew she would never have sex till she was married, you knew that this is the bargain deal from the start, you have chosen to take to that commitment and be loyal and now you have broken it.
I don't know how strong both of you are, but if its enough to make this work. Then i do wish you luck. you seem sincerely sorry for it and have admitted to the betrayal to her.
I hope in the future for both of you it works out. I suppose reading through this thread you do seem like a genuine guy, who feels guilt and remorse for the mistake he did. Admitting to it and fully taken responsibility for it, not people can do that....some people can be oblivious that their actions can effect people in a bad way and get away with it........without knowing they put a person through hell.