How did Felicia kill the dog?

Felicia killed the dog by dosing its meat in laudanum.

“I went to the lotus pond,” Felicia said finally. “I was … so angry … at how they treated you at the birthday party. I wanted to kill that abomination El Patron keeps at his heels.”

Matt felt cold. He’d had no idea how much Felicia hated him.

“But I had to be satisfied with … that filthy, slavering rat María called a dog. I keep a small amount of laudanum for my nerves.” She keeps about enough to wipe out a city, Matt thought.

“So I poured one of … my bottles on the hamburger that idiot clone left behind. ‘Come here, Furball,’ I called. He didn’t want to leave his bag, but I … dumped him out … on the meat. He ate the whole thing.”