You are so right, she is very irrelevant. Remember, it takes two to tango, you read the messages and although he never replied ‘I love you too’ he was definitely entertaining her feelings, deep feelings for him. Yeah, he would say whatever to let you think that they will stop communicating but all I can say is that you have to decide if you can live with knowing he may or may not have feelings for her. You have to either forgive him fully or none at all. Bringing it up after you have moved past it will only aggrevate him. And him saying you broke his trust is just him trying to take the blame off him. He broke your trust too! Dont sell yourself short for the familiar feeling of love and acceptance. You deserve the best, and you deserve loyalty and respect.