Hey guy!
You may or may not like what I'm going to tell you. I do some dream interpretation for people now and again, when there's a demand for it. Everybody has a theory about dreams of course, and I tend to go along with old Carl Jung(check him out on the web, an amazing thinker!). The way that dreams seem to me, they're basically all about the dreamer.
The dark girl is your own dark feminine side, that side of EVERY man where the "spark", that you were referring to having LOST, lives and breathes and COMES into full existence. She's a part of your own soul, inviting you to experience a deeper sensuality and sexuality, perhaps, that will lead to your ex being just one of the lass's who need to see you all of a sudden.