Why did you do anything with her, knowing she used to be into you? This just seems like you didn't think about shit, and I don't see any other comments ripping into you. Yea, it was a mistake, but it was a mistake for you. For someone else it was almost what they've been wanting for who knows how long, and then being led on. Think about them, and how you've treated them. They deserves honesty and you should be very sure to learn from this. We all make mistakes but fucking around with someone else's feelings when you know it won't go well is a really fucking stupid move.