There's trouble in rodeoland and she's wondering if you're still available. She wants to get back together. When we think back on old relationships, we often remember the good stuff and gloss over the bad. You are right to not respond.
An ex of mine called me out of the blue about two years ago. We'd had no contact for about two years before that. She said that she wanted me to know that she had moved up to Baltimore from Orlando (now within driving distance to Conn), and I'm sure she was interested in rekindling the flames, but I was in a committed relationship at the time and told her so when she asked. She was HOT, HOT, HOT, but also CRAZY, CRAZY, CRAZY, so while it would have been tempting if I had been available, I would have thought with the right head and made the correct decision.