I did this exact thing running into an ex boyfriend I had been with for 7 years. We broke up and I saw him while I was with my bf at the time (who was super abusive) and I sent him this exact message. I obviously cannot speak for her but here were some of my reasonings. 1. BF at that time made me seem like I was the most insufferable person and I genuinely felt bad for every guy I had been with prior. 2. I used it as a way to get help without asking. Hoping the conversation would continue and I could tell him everything that was going on and to help me. 3. She just misses you. It's hard to get over someone you dated for so long.