I think you're over thinking it. It sounds like a lot of time has passed and she's gained a new perspective on the whole situation and wants you to know she doesn't have any animosity towards you anymore. You guys had a long relationship so I think it's good that she took the time to reach out, say hello and let you know she holds no grudge. The fact that it took 3 years, well you guys both moved on and went your separate ways so time flies as we all know. If you two dated for a month or so and she reached out to you then that's different. But it was a long relationship and I think this is a positive things. Maybe there is something more there and both of you are in different (better) places and could try again or maybe it turns into nothing more than a 1 time get together but you both leave knowing you at least let go of the past. I think it's all good. As long as you aren't going into it expecting too much.