Thank her for being honest. She told you she didn't feel content with the way things are. Most would've chosen to hide this from you, hoping to avoid conflict or the awkwardness that would follow. Then they would've likely proceeded to cheat. But she cared enough to share her sense of dissatisfaction. Now you must respect her courage and accept that this isn't something you can fix. It's her problem and her responsibility. A good relationship is only possible when both spouses can be happy on their own. Hence, she will need to figure out what's making her feel discontent. So, you should end this relationship. If you're not willing to, it'll end eventually. Your girlfriend was correct to propose an 'open' relationship because it seems you rely on her for your happiness. Honestly, it'd be better if you two took a 'break' to find happiness on your lonesomes. An 'open' relationship isn't likely to fix that. Anyways, mad respect to your girlfriend. She's a real G. Honesty is a value that's hard to find in people nowadays, so I have nothing but respect for anyone who tries to show it.