How many harlequins do you have?
What's the set up?
I had water too hard for the eggs to hatch the last time I kept them, but they would lay eggs under Cryptocoryne leaves, which would keep them from getting egg bound. You'd need slender bodied males, plants with the right leaves and regular weekly 25-30% water changes to get them going. They spawned at around 26 degrees.
You could give her a short epsom salts bath, outside the tank but in equal to the tank temperature water. That can stimulate a release. You would have to look up the ratio of salts to water. I haven't done that in ages. A 20-30 minute bath would be a start.
And look at how much you feed, and reduce it a bit. Almost all of us overfeed our fish.