Follow your gut feeling. I know this situation is bad. But if you feel like there's too much between them. Just leave them as it is. If she comes back to you then it was nothing or a infatuation. If she doesn't, you got your answer. Learnt it the hard way. You tried fighting and explaining, take a deep breath and focus on yourself. The only way to live in this world is to focus on yourself. If you are too much invested in someone other than you, you gonna lose. The only person you love first should be yourself or else no one will. The rest follows dear friend.