How does the Dust of Broken Hearts choose its love target?

Question

In Willow, one of the brownies (Franjean) carries a bag of Dust of Broken Hearts. Whoever inhales it can expect to soon madly fall in love with... who, exactly?

• When Rool the brownie inhaled it, he fell in love with a cat (different species, unclear gender). That was literally seconds after Rool inhaled the dust, and seemed to be literally the first person he saw ;
• When Madmartigan inhaled it, he fell in love with Sorsha (same species, opposite gender), but that was after a few minutes during which he also laid eyes on the brownies, Willow, and Elora Danan.

The obvious out-of-universe reason for these love targets is "it's funnier that way" (and it is), but I'm wondering if there's an in-universe explanation as to why Madmartigan didn't fall in love with someone before Sorsha? I've only seen the movie, not read any novels or interviews; maybe it's explained there if it's a matter of...

• Gender? I don't know about the cat, but Sorsha was the first female Madmartigan saw; admittedly after Elora Danan, but Elora Danan is a baby. It'd seem awkward if Madmartigan hit on a baby;
• Activation delay? Madmartigan and Rool seemed to have inhaled a comparable amount of dust, but maybe it took longer for its effects to be triggered as Madmartigan is taller/heavier than a brownie?
• something else?

Answer 1

The implication from the film's official novelisation is that the 'Dust of Broken Heart' makes you fall in love with everything and everyone you look at, indiscriminately.

• Rool the brownie fell in love with the cat because it was there.

  Dust from the pouch spilled out into his eyes, and when he opened them again he found himself in love with a yellow cat crouched under the table. “Oooo,” he crooned. “You’re so beautiful!”

MadMardigan, who took a much bigger dose, falls in love with (respectively),

• Absolutely everything

  Grinning stupidly, in love with everything,

• A dirty mule

  “Adorable! Lovely!” Starry-eyed, Madmartigan tottered toward a mud-caked and sneering mule.

• An ugly man

  “Ah! Love of my life!” Arms wide, Madmartigan tried to embrace a swarthy and hungover trooper who was just then lurching out of his tent. The man cursed and reeled back inside.

• and finally Sorsha, to whom he was already attracted, at least in a sexual way.

  Even if one had not been bedazzled by the magical fairy dust, it would have been hard to believe that she was Bavmorda’s daughter. It would have been hard to imagine her engaged in the business of death. She radiated life—glowing, pure, and exuberant.
  Madmartigan crept up and kissed her gently on the cheek. “I love you,” he said.

All of the above were right in front of him when he fell in love with them.

Answer 2

It probably goes by the person's natural inclination (the same species, sexual orientation and so on).

As for the cat? Well, cats are the exception, they're awesome, it's easy to fall for them. I bet Madmartigan would've fallen for it too.